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and Enemies 

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OUR INSECT FRIENDS AND ENEMIES 












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1. The oriental roach or " black beetle " : male. 

2. The oriental roach or " black beetle " : female. 

3. The German roach or " croton bug " : male. 

4. The German roach or " croton bug " : female, with egg case. 

5. Egg of bed-bug. 

6. Bed-bug. 

7. Caterpillar of a " clothes-moth " in its case. 

8. One of the common " clothes-moths." 

9. The " buffalo moth " or " bug." 

to. The parent beetle of the " buffalo moth." 

11. Egg of a flea. 

12. A flea larva. 

13. The common dog flea. 

14. The little red house-ant. 

All of the flgures are very much enlarged and most of them were re-drawn 
from the Bulletins and Reports of the Division of Entomology, U. S. Department 
of Agriculture. 



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SM' OUR INSECT FRIENDS 
AND ENEMIES 

THE RELATION OF INSECTS TO MAN, TO OTHER 
ANIMALS, TO ONE ANOTHER, AND TO PLANTS 

WITH A CHAPTER ON 

THE WAR AGAINST INSECTS 



By 



JOHN B. SMITH, Sc.D. 



PROFESSOR OF ENTOMOLOGY IN RUTGERS COLLEGE; ENTOMOLOGIST TO THB 

NEW JERSEY AGRICULTURAL EXPERIMENT STATIONS; NEW JERSEY 

STATE ENTOMOLOGIST; MEMBER AND FELLOW OF A. A. A. S.; 

N. Y. ACADEMY OF SCIENCES; ENTOMOLOGICAL 

SOCIETY OF AMERICA ; ETC., ETC. 




PHILADELPHIA &- LONDON 

J. B. LIPPINCOTT COMPANY 

1909 



Copyright, 1909 
By J. B. LippiNcoTT Company 



Published April, 1909 



Ehctrotyped and printed by J. B. Lifpinc^tt Companv 
the fVaihington Stuart Press, Philadelphia, U. S. A. 



FOREWORD 

Nothing in this world of ours exists to, for or by 
itself alone. Every living creature depends upon some 
other form of life, or upon inorganic matter and is, in 
turn, the dependence of others that find it useful or 
essential for continued existence. And as inorganic 
matter is, after all, the base of organic matter as we 
know it, plus the addition that makes it organic and 
whose nature we do not yet know, so in due course all 
organised forms again return to their lifeless constituents. 

Every living thing, then, has relations to many 
other living things and some of these relations, so far 
as insects are concerned, it is my object to present. 
I need hardly disclaim any attempt at completeness; 
but so far as the presentation goes it claims accuracy. 
A large proportion of the facts have been personally 
observed or verified, others are common knowledge 
and all are based upon the observations or records of 
scientific investigators. 

Some of these relations of insects to the welfare of 
man have been but recently worked out and are imper- 
fectly known; yet enough has come to the general 
information to arouse a decided interest in these long 
despised creatures. Their presence or absence from our 
midst may make all the difference between sickness 
and health, irritation and comfort, poverty or wealth, 
or, on the other hand, wealth and poverty. They make 
some regions uninhabitable that would otherwise be 
attractive as sites for homes and, altogether, their 
influence upon humanity, directly and indirectly, is 
vastly greater than is generally realized. 
5 



ACKNOWLEDGMENTS 

Of the figures illustrating this work, the following 
were drawn for me by Mr. John A. Grossbeck, my as- 
sistant, from originals or modified from published 
sources: i, 4, 5, 6, 7, 8, 10, 11, 13, 18, 19, 20, 22, 24, 
34, 41, 61, 64, 65, 66, 67, 68, 70, 71, 80, 81, 87, 89, 92, 
93. 94, 95- 96, 104, 107. 

From the publications of the Entomological Division 
of the U. S. Department of Agriculture the following 
were obtained, either as electrotypes or as copies from 
the prints: 9, 49, 63, 77, 91, 98, 100, loi, 103, no, 112, 

113- 

From the New Jersey Agricultural College Experi- 
ment Station I obtained blocks for figures 48 and 99. 

The other blocks are by courtesy of the J. B. Lip- 
pincott Company from my "Economic Entomology," 
where their original source is stated; but a number of 
them have been somewhat reduced in size. 



CONTENTS 



CHAPTER PAGE 

I. Insects in their Relation to the Animal King- 
dom 9 

II. Insects in their Relation to Plants as Bene- 
factors 2 1 

III. Insects in their Relation to Plants as De- 

stroyers 40 

IV. Insects IN their Relation to Each Other 84 

V. Insects in their Relation to the Animals that 

Feed on them 130 

VI. Insects in their Relation to Weather and Dis- 
eases THAT Affect them 138 

VII. Insects IN their Relation TO Other Animals. .. . 153 

VIII. Insects in their Relation to Man: as Benefac- 
tors 185 

IX. Insects in their Relation to Man: as Carriers 

OF Diseases 199 

X. Insects IN their Relation TO the Household.. . 217 

XI. Insects in their Relation to the Farmer and 

Fruit-grower 249 

XII. The War on Insects 271 

Index 309 



OUR INSECT FRIENDS 
AND ENEMIES 



CHAPTER I 

THEIR RELATION TO THE ANIMAL KINGDOM 

If we examine any insect, large or small, in any 
save the egg stage, we note at once that it has its skeleton 
on the outside of the body. Not much of a skeleton in 
some cases, e.^., a caterpillar, a slug or a maggot; a 
very resistant and rigid shell or body wall in others, as 
in some beetles which may be run over by a heavy 
wagon wheel without being any the worse, or may pass 
unchanged through the digestive system of a toad. 
In any event it serves for the attachment of the muscles 
on the inside, and they are thus protected, instead of 
sheltering and protecting an inside bony framework as 
in man and other vertebrate animals. 

It will be further seen, especially in the simpler 
forms, that the body is made up of successive rings or 
joints, more or less similar in the primitive types, often 
very unlike in the higher orders, and that the legs also 
are made up of a number of parts or segments. These 
characters place the insects with that great section of 
the animal kingdom known as Articulata, which includes 
everything from an earthworm to a lobster, and more 
narrowly restricts them to the Arthropods, which have 
jointed legs, and thus exclude the worms; but still 
leaves the lobster as a relative. 
9 



lo INSECTS 

Matters now become a little more difficult; but if 
we continue our examinations by comparing a lobster, 
a spider and a beetle, we find that the latter has a 
distinct head, separate from the rest of the body, while 
in the others the head and middle section of the body 
form a single mass known as a " cephalothorax. " Our 
beetle also will be found to be breathing from the sides 
of the body through a series of ringed tubes known as 
trachea: and this makes it a Tracheate — an honor that it 
shares with centipedes or myriapods. Finally, if we 
persist in our policy of exclusion, we leave as true 
insects only those forms that have no more than three 
pairs of jointed legs, attached to the thorax or middle 
region of the body, the body itself made up of no more 
than thirteen obvious rings or segments, grouped into 
three regions, the head, thorax, and abdomen, contain- 
ing respectively one, three and nine segments. 

We are now ready to define an insect as an articulate, 
arthropod, tracheate hexapod; but it will be equally 
correct and much easier to say that it is a ringed ani- 
mal, with six jointed legs, breathing by means of air 
tubes or trachea;; this definition applying more particu- 
larly to the adult stage, and only to the adult stage of 
many of those having a complete metamorphosis. 

This method of breathing, by the bye, carries with 
it a modification of the circulating system. The air 
being carried in tubes to all parts of the body, there is 
no need for lungs nor for any system of veins or arteries. 
The blood simply flows about in the interstices of the 
body cavity, kept in motion by a tube-like heart, divided 
into chambers, which lies just under the back or dorsal 
surface, and oxygen is taken up from the tracheaj any- 
where in its course, while the products of digestion are 
taken up from the specialized cells about the digestive 
system. And, after all, the process of maintaining life 



RELATION TO ANIMAL KINGDOM 




12 INSECTS 

and activity is much the same among insects as it is 
in the higher animals, although the method is some- 
what different. The blood is equally the agent for 
transporting nutritious material to whatever point it 
may be needed, and the oxygen to burn out waste 
products is as essential. 

Under the microscope, insect muscle is not so very 
different from that of man: it has similar transverse 
striations, and contracts and extends in a similar 
manner, but, nevertheless, there is no chance of con- 
fusing insect with vertebrate muscle. This muscular 
system is under the control of a nervous system which 
is very highly developed in detail, but consists essen- 
tially of a double cord extending from one end of the 
body to the other, lying just above the under or ventral 
surface and furnished with a series of enlargements or 
ganglia, of which that lying in the head and termed the 
brain is the largest, although it exercises no such dominant 
influence as does that organ in the higher vertebrates. 

There is quite a difference, of course, among insects, 
in the amount of specialization in this nervous system. 
In some and especially in larval forms all the ganglia 
are similar in size and appearance, and there is one for 
every segment; in others the tendency to centraHza- 
tion is marked, all the thoracic ganglia being united into 
one, while in the abdomen two or three of the posterior 
gangha join in the control of the reproductive system 
and the various accessory parts connected with it. The 
thoracic centre controls the organs of locomotion and a 
paralysis that is practical death results immediately 
when this ganglion is cut, whereas we can cut off the 
head and abdomen, of a house-fly for instance, without 
interfering with its power to use legs or wings. This 
fact was known to the digger wasps long before the 
entomologist knew it, for when such a digger wishes to 



RELATION TO ANIMAL KINGDOM 13 

quiet its prey before carting it home, the sting is aimed 
at this very gangUon with instantaneous results. 

As to senses, the insects have all those of other 
animals and perhaps more, too; but developed in an 
altogether different way and to a very diverse extent. 
Insects see and have the most complicated kinds of 
eyes known, as well as almost the simplest in existence. 
Some species are sensitive to rays of light which man 
cannot see at all and some species certainly seem to 
see better at night than during the day. But, on the 
other hand, it is doubtful whether they see at all dis- 
tinctly or can recognize form and color when not directly 
connected with their life-needs. So they can hear; 
some of them very acutely, and ears are by no means 
confined to the head: they may be on the feet, the body, 
the abdomen or on the antennae, and it is believed that 
they hear sounds so high in pitch that they are beyond 
the reach of our senses. Nevertheless it is almost equally 
certain that they are probably incapable of discriminat- 
ing between sounds, and of really recognizing any but 
those connected with the sexual calls of their mates or 
perhaps the noises made by their prey and possibly 
their enemies. Insects certainly have the sense of taste 
and some of the most elaborate taste organs are found 
in species feeding on the vilest excrementitious material. 
Perhaps the less we say on this point the better, 
unless it is to suggest that there are gustatory possi- 
bilities that man is utterly incapable of appreciating. 
Insects smell, and this sense is most acutely developed. 
The male seeks and finds the female almost entirely 
by this sense even when she is carefully and intentionally 
hidden from sight, and both sexes find their food by 
this sense more often than by sight: and that is particu- 
larly true of those forms that feed on fermenting or 
decaying matter. Insects feel, no doubt, and the tac- 



14 INSECTS 

tile sense is popularly and probably with justice located 
chiefly in the antennae; but the mouth feelers or palpi 
are also organs of touch and tactile hairs may occur on 
any part of the body or its appendages. No one insect 
species has all these senses equally well developed, and 
few have more than one or two really so specialized as 
to be conspicuous. There are more, indeed, which have 
none of them more than rudimentarily present and 
probably a fairly well-developed general sense of per- 
ception is enough for the majority. Such a sense enables 
the insect to recognize the vibrations that mean food, 
a mate and a place to oviposit and that is all that is 
really necessary to enable it to fill its place in life. As 
to that tactile sense that implies a recognition of what 
we know as pain, I believe it to be very feebly developed. 
I do not indeed assert that insects are insensible to pain ; 
but all observations indicate that they appreciate it 
very little and very temporarily: real suffering I do 
not believe them capable of at all. 

An interesting question that is often raised in this 
connection is whether insects reason or whether all 
their actions are instinctive. I do not believe that 
any one can study insects at all closely without crediting 
them with a certain amount of reasoning power. Some 
species do such incredibly stupid things occasionally 
that it would be a libel on instinct to charge it with such 
actions, and often specimens of the same species will 
do things so differently that individuality and ratio- 
cination must be accepted as accounting for the differ- 
ence. To be sure it is not a very high grade of intelli- 
gence that is manifested, using our own attainments as 
a standard; but it is such a grade as brings out the 
difference between individuals and species and enables 
one to do well what the other fails in, habitually. It is 
in the Hymenoptera and especially among the social forms 



RELATION TO ANIMAL KINGDOM 15 

that this intelhgence is best manifested; but I have noted 
it in the majority of the species that I have observed at 
all carefully in the open, under natural conditions rather 
than in the laboratory in artificial surroundings. 

Insects are as a rule prolific breeders, although 
there is a great difference between them in this respect: 
some multiply only ten-fold in the course of the season, 
while in others the capacity is 1,000,000,000 descendants 
in the same period. No one has actually counted that 
number, of course, but we have counted the number 
bom to a single pair and determined the number of 
broods to the season; so it is a mathematical certainty, 
even if, as a matter of fact, probably no one pair ever 
matured all its offspring for as many successive genera- 
tions as are required to produce such a result. 

In their development there is considerable variety, 
but as a rule they pass through four more or less distinct 
stages: this being called transformation or metamor- 
phosis, while the various stages are also called instars. 

The first, or egg-stage, is usually quiescent and gen- 
erally passed outside the insect body ; but in some cases 
it hatches within the ovary of the mother and young are 
bom alive, as in many plant lice and scale insects. Spe- 
cies may therefore be oviparous (egg-bearing), or vivip- 
arous (live-bearing), the latter also termed larviparous. 

The second, or larval stage, is that which hatches 
from the egg, and it may or may not be like the parent. 
In the grasshopper, for instance, we can recognize it 
as such, no matter how recently hatched; but in the 
minute caterpillar, just out of the shell, no resemblance 
to the butterfly can be traced. The larval stage is the 
period of growth: the insect feeds to the limit of the 
elasticity of its integument or outer skeleton, then 
sheds this skin or "moults," and repeats this process 
until it has reached its limit of size. 



i6 



INSECTS 



It may be well to say just a few words as to this 
outer skin which forms so important a feature in the 
insect structure. It is soft yet resistant, and may 
become so resistant that it is almost impenetrable to 
corrosives or oils and with difficulty to be punctured 
with needle or knife. It all depends upon the amount 
of chitin deposited in the tissue and chitin is a secre- 
tion from the lower layers of the cuticle, resembling 
horn in texture and somewhat in qualities. No matter 




Fig. 2. — Moulting of a grasshopper: a, nymph ready to change; b, the skin 
split along the back and the adult emerging; c, continues the process, and at d, 
the insect is drying out. 



how soft the body wall it contains some chitin and as 
this is not elastic, there is a limit beyond which it cannot 
be stretched. When this limit is reached a new skin 
forms beneath the old one which, thereupon becoming 
lifeless, splits and permits the larger next stage to escape. 
This sort of change is found also in the crustaceans, 
and in some of the reptiles. 

The third, or pupal stage, may be a period of rest 
or of continued activity, depending upon whether the 
species has a "complete" or an "incomplete" meta- 
morphosis. Returning again to our young grasshopper, 



RELATION TO ANIMAL KINGDOM 17 

usually called a "nymph" rather than a larva, when 
this has become ripe, it develops wing pads or rudimen- 
tary wings ; but continues its feeding as in the preceding 
stages until the period when it moults for the last time 
and changes to the adult or fourth stage. It thus 
develops continuously, without conspicuous change of 
form, and the metamorphosis is incomplete. Our 
caterpillar, however, after moulting as often as needed 
to obtain full size, changes into a 
nondescript creature bearing no close 
resemblance to its former nor to its 
future stage and remains in this 
"pupal" or "chrysaHs" form while 'fk-,.3. -Sect, on through 
the caterpillar structures are disin- insect crust showing lay- 

ers of chitin at c, the cel- 

tegrated and re-tormed mto butter- luiar layer at h, and the 
fly parts. This is a complete trans- basal membrane at ;,. 
formation, in which almost no part 
of the larval structure remains unchanged, and even 
the method of feeding may become completely reversed: 
indeed, in some cases the adults never feed at all, 
depending entirely upon the supply stored by the larva 
to mature the reproductive cells or eggs. 

Among themselves insects differ as much in appear- 
ance and habits as they do from their more remote 
relations. They are found wherever life is capable of 
existing at all, and there is no organic substance known 
which, in one stage or another, is not food for some 
insect. They are moderately numerous, some 200,000 
different kinds being already known and described, 
with the reasonable certainty that we have not yet 
discovered much more than one-half of those that exist. 

There are some that never become winged; that are 
soft-bodied in all stages, live usually in damp places 
and are simply organized: these are the Thysanura, in 
^J which the mouth structure is not well developed. 



i8 INSECTS 

A very decided advance is found in those insects 
that gain their food by sucking it through a jointed 
beak by means of slender, bristle-Uke lancets in all 
stages; and these are the Hemiptera or true bugs. 

Grasshoppers, roaches, crickets and the like have 
the hind wings folded in longitudinal plaits, laid straight 
under the covering primaries, and are hence called 
Orthoptera. They chew their food and are often trouble- 
some to the agriculturist. 

Another large series has the wings thin, transparent, 
usually of good size, with numerous longitudinal and 
transverse veins like a net or reticule and hence called 
Neuroptera. This is the most primitive of the winged 
orders of biting insects, and shows a great diversity of 
forms and grades of development. The dragon flies 
serve as a well-known illustration of one type. The 
very general definition of the order here given covers a 
series of remnants that are elsewhere more particularly 
specified. It was in the Neuropterous or net-winged 
type that the great break-up among the mandibulate 
insects occurred and variation ran in many directions. 
Some of the lines flourished for a little time only; they 
proved ill adapted to their surroundings and survive 
only by a few families and genera in which the species 
are usually well fixed and easily distinguished. Others, 
well suited to live, proved barren when it came to adapt- 
ing themselves to new or a variety of conditions. These 
are fairly numerous even now in families, genera and 
species; but their limit of adaptation is reached and 
they are shoots from which no further branches may 
be expected. From the other lines the modern domi- 
nant orders developed which, rich in forms, show 
species capable of living under the greatest conceivable 
variety of conditions. 

The Coleoptera or beetles are known by the hard 



RELATION TO ANIMAL KINGDOM 19 




Fig. 4. — The orders of insects: i, a bristle tail and 2, a spring tail, are Thysa- 
nura; 3, a dragon fly and 4, a Psocid, illustrating Ncuroptera; $, a grasshopper, 
illustrating Orihoptera; 6, a shield bug represents Hemiptera; 7, a ground 
beetle shows Coleoptera; 8, a butterfly, illustrating Lepidoptera; 9, a horse-fly 
represents the Diptera, and 10, a bumble-bee, the Hymenoptera. 



20 INSECTS 

or leathery fore-wings, beneath which the membranous 
secondaries are transversely folded. They gain their 
food by chewing, in all stages, although the early or 
larval forms are usually altogether unlike the adults. 

The T.epidoptera include the butterflies and moths, 
known by the scaly covering of the wings. The scales 
appear as fine, dust-like particles that are easily rubbed 
off; but under the microscope show great differences 
in form and color. In this order the mouth parts of the 
adult are modified into a coiled tongue capable of sipping 
liquids only; but in the larval stage the caterpillars are 
voracious devourers of plant and other tissue. 

Bees, ants, wasps and the like belong to the order 
Hymenoptera, in which the wings are transparent, with 
few and often no veins; never reticulated. Many of 
the species are of extreme interest because of their 
social habits and organizations, and the honey bee is of 
direct benefit to man in more ways than one. 

Finally come the flies ; differing from all other insects 
by having only one pair of wings, whence their ordinal 
name Diptera. We shall have more to say concerning 
some of their species and development elsewhere. 

The insects as a whole are at the top of the line of 
development in the Articulata: they diverged early 
from the worm-like ancestors and their remains, already 
well developed, are found in the earliest fossil-bearing 
strata. At the present time there are more species of 
insects than there are of all other species of animals 
taken together, and in number of individuals they are 
unapproachable. The class as a whole is yet a growing 
one and both genera and species are in some orders 
unfixed and in process of formation. There is no better 
field for the study of animal variation, and the problems 
imposed upon us by them have scarcely begun to be 
appreciated. 



CHAPTER II 

THEIR RELATION TO PLANTS AS BENEFACTORS 

While, in a general way, insects frequent plants 
merely to feed on them, yet this feeding is not neces- 
sarily destructive and may even contain an element of 
advantage. Hence we find that, far from developing 
structures to repel, many plants produce attractive 
flowers and secrete nectar as an invitation to insects to 
call upon or visit them. 

Flowering plants as a rule have two kinds of sexual 
organs: the pistil connected with the seed or female 
element, and the stamens, producing the pollen or male 
element. Fertilization takes place when the pollen or 
male element is brought into contact with the receptive 
surface of the pistil, and this pollination may be produced 
in many different ways. Sometimes the same flower 
has both pistil and stamens, and the pollen from the 
latter may be discharged so as to come into immediate 
or direct contact with the former. But this is not 
always the case, for the pistil may not reach the recep- 
tive condition until after all the pollen has been removed 
from the stamens and, on the other hand, the pistil 
may become receptive before the pollen on the same 
flower is mature. In such cases there must be polli- 
nation by some outside agency. Many flowers are of 
one sex only, i.e., either pistillate, bearing female 
organs only, or staminate, bearing male organs only: 
and sometimes an entire tree or plant may bear flowers 
of one sex only. Here again pollination by some carrier 
is necessary and among the carriers the most active 
agents are the wind and insects. 



22 INSECTS 

Plants which depend upon the wind for poUination 
usually produce a light pollen in great quantity, so that 
at times the air may be full of it. Plants which depend 
upon insects for pollination may produce much or little ; 
but it is usually somewhat sticky so as to adhere readily 
to the body or vestiture of the visitor. And as insects are 
not altruistic enough to call on the flowers merely to 
benefit them, some sort of attraction must be offered 




-Sepdl 

Fig. s. — Section through a flower, illustrating the reproductive parts. 



to invite the visits. This attraction may be in the shape 
of honey or nectar for those species who seek for them- 
selves alone, or for their progeny; or in the shape of 
pollen suitable for use as food directly or in preparing 
food for the young of the visitor. 

Where nectar alone is relied upon to attract, it is 
usually stored so as to compel the insects to come into 
contact with the reproductive organs in their efforts to 
reach it; and in such cases, not infrequently, the flowers 
are modified to invite special kinds of insects only. 



THEIR RELATION TO PLANTS 23 

For instance, the clovers are especially adapted to 
attract long-tongued bees; flowers like the Petunia, 
the evening primrose or the jimpson weed attract the 
hawk-moths, whose long, flexible tongues reach to the 
nectar cups at the very bottom of the deep florets. 




Fig. 6. — a. Yucca flower with moth in position, ovipositing; b, Pronuba gath- 
ering its pollen mass; c. head of Pronuba from side showing the maxillary 
tentacle; d, tip of the ovipositor. 



So far as the insects are concerned the pollination 
is a mere incident in most cases: it occurs because the 
flower is so built that it must occur when the pollen or 
nectar is gathered. But there is at least one case in 
which it appears almost as if the insect acted intel- 
ligently, with a definite purpose in view, and the 
demonstration of this case we owe to the careful obser- 



24 INSECTS 

vations of Dr. C. V. Riley, erstwhile Entomologist to 
the U. S. Department of Agriculture. 

The flowers of the species of Yucca are absolutely 
incapable of self- or wind-pollination, and the stigma is 
so situated that no ordinary insect visitor can reach it 
in a casual search for food. In some localities, it was 
observed that the common Yucca or soap-weed never 
produced seed and that wherever seed was produced, 
almost every pod was infested by a little caterpillar 
that destroyed a greater or less percentage of the seeds. 
The parent of this caterpillar is a small white moth, 
the Pronuba yuccasella of Riley, in which the mouth- 
parts are curiously modified and utterly unlike those of 
any other moth species that we know. At the sides of 
the ordinary tongue there are developed a pair of flex- 
ible processes set with little pegs and spines, and capable 
of being coiled Hke the tongue itself. When the female, 
which alone has these processes, is ready to lay an egg, 
she enters a Yucca blossom, gathers a little mass of 
pollen, rolls it into a ball, carries it by means of the 
coiled processes to the pistil, and rams it down so as 
to bring it into direct contact with the receptive surface. 
Not until this has been completed does she turn and 
then, into the ovary or embyro seed pod, she forces an 
egg by means of a slender, sharp-pointed ovipositor. 
She is now ready to repeat the process on another flower 
and she does repeat it until her stock of eggs is exhausted. 
Here we have a deliberate pollination preceding ovi- 
position, as if the insect knew that it would be useless 
to lay an egg until the possibility of development in 
the seed pod was assured. 

This peculiarity, though confined so far as we know 
to the genus Pronuba, is not confined to one species 
only. There are a number of Yuccas in the country, 
including the giant or tree Yuccas of the southwest, 



THEIR RELATION TO PLANTS 25 

and for every species of Yucca there is a species of Pro- 
nuha. Surely a most wonderful adaptation of insect and 
plant, neither of which can now exist without the other. 

And yet, while the adaptation is not so specific, nor 
the evidence of design so apparent, the dependence of 
red clover upon long-tongued bees is not less absolute. 
Australia has no native bumble-bee, and red clover was 
unknown there until the colonists began to cultivate it. 
There was no difficulty in making crops of forage; but 
it would not seed. Importing seed annually was expen- 
sive and, naturally, the Australians were anxious to 
raise their own. This led to a study of the reasons for 
the failure, in the course of which the dependence of the 
plant upon bumble-bees was established. The remedy 
was obvious, and now European bumble-bees disport 
themselves among the Australian red clover, seed is 
plentiful, and interference with bumble-bees is a crime — 
as it should be rated everywhere. 

Bees, by the way, are the most universal pollenizers, 
and are highly specialized for that purpose. All bees 
are more or less hairy: sometimes conspicuously so, a 
dense woolly clothing appearing all over the body; 
sometimes sparsely, the hair being often localized. But 
whatever the bee, and however scant its clothing, the 
hair is always compound: spurred, branched or even 
plumose. In some series it is so strikingly characteristic, 
that from the hair alone, the genus to which a bee 
belongs can be determined with reasonable certainty. 
In all modifications and adaptations, be they small or 
great, the pollen-gathering function is always attained: 
for bees need pollen in their domestic economy. Most 
insect mothers have no more care for their offspring 
than to place the egg in some position where the larva, 
when hatched, will find food. In the Hymenoptera, to 
which the bees belong, storing food upon which the 



26 INSECTS 

larva feeds is a common occurrence, and the larva, 
when hatched, finds surromiding it sufficient nourish- 
ment to bring it to maturity. In the social forms, 
matters have developed yet further, and the larva does 
not even feed itself: it is fed by the mother or a nurse, 
and its food is prepared beforehand; either a mixture 
of pollen and honey, or fragments of insects mixed 
with salivary secretions of the adult. And so bees need 
pollen as food for their larvae, and upon the mothers or 
females falls the burden of gathering and storing it. 
For convenience we consider as females those sexually 
undeveloped forms in the social species which we know 
as workers, and in that sense all the female bees are 
supplied, not only with gathering hairs, but with some 
sort of structures to carry the pollen. In the common 
hive-bee the inside of the first joint of the hind foot or 
tarsus is modified into a curry-comb-like structure for 
cleaning the pollen grains out of the hair, and the out- 
side of the hind tibia is provided with a fringe of long 
hair forming a basket into which the pollen is packed 
for transportation. In other bees other parts of the 
legs, of the breast, or even of the abdomen are provided 
with means of transporting pollen loads, and so after 
a visit to the first flower the bee is fitted for its mission 
of fructification, which occurs as a mere incident in the 
gathering. 

There is no group among the insects that is more 
interesting as a subject for study than that containing 
the bees. Not only are the structures of adaptation 
very beautifully developed for their purpose; but their 
life history is often of intense interest. On the honey 
bee alone we have not only the vestiture, the pollen 
carrier and the brushes that clean out the pollen from 
the hair; we have, in addition, the antenna-cleaner 
on the fore leg and the complicated mouth parts. The 



THEIR RELATION TO PLANTS 



27 




Fig. 7. — Bee structures 



honey bee, pollen loaded; 



b. mouth parts of a long- 
d, wax cutter and curry. 



tongued bee; c, hind leg of bee showing pollen earner^ v ,f hnmble 

rongucu u , , - antenna-cleaner of foreleg; f. hair of bumble 



comb of ist joint of hind tarsus 

bee; g. hair of Melissodes; h. hair of Mcgachtle; 



hair of Xylocopa. 



28 INSECTS 

antenna-cleaner is a little notch on the inner side of the 
basal joint of the front tarsus, set with fine teeth and 
closed by a spur from the end of the fore tibia. When 
the bee desires to comb out the vestiture of one of the 
feelers, the fore leg is brought up, the notch is hooked 
over the stem at base, the spur is brought to the lock, 
and at a single sweep the entire series of joints is brought 
into condition. It is all very simple and very neat, 
and could not be better adapted for its purpose if 
designed by man himself. The mouth structures which 
are also kept in condition with this apparatus merit a 
little further attention. 

I have already alluded to "long-tongued" bees and 
this has carried with it the suggestion that there was a 
difference in that respect. As a matter of fact there is 
every intermediate form between the tongue of the 
bumble-bee, more than half as long as the insect itself, 
and the little digger bee, whose labium or lower lip does 
not extend beyond the edge of the mouth. It is not 
always easy for the novice to recognize to which division 
a bee under observation belongs, because the long tongue 
is usually hinged, and may be drawn back against the 
breast in such a way as to be protected from danger of 
injury. When fully extended the mouth has, laterally, 
a pair of very well-developed mandibles, which usually 
serve more as tools in building homes than as organs 
for securing food. Between these mandibles, and com- 
pletely separated from them, is a pair of sheath-like 
structures which are generally pointed at the tip. These 
are the maxillae, which are not of much active use, 
though they are the organs by means of which ripe 
grapes and other fruits are occasionally punctured 
when normal supplies are scarce. In the very centre is 
the flexible tongue itself, ringed in structure, with series 
of hairs round about it, and a little button of hair at the 



THEIR RELATION TO PLANTS 29 

tip. This is the structure that is forced down into the 
very heart of the flower and forms a lapping organ, by 
means of which every particle of nectar may be secured. 
The bee is not really a sucking insect at all ; but gets its 
food by lapping somewhat after the manner in which 
a dog laps water. 

Only the honey gatherers have tongues of this type. 
Bees and honey are usually associated, but as a matter 
of fact many kinds gather no honey at all, and very 
few of them store it. In the species in which there is no 
elongated central tongue, this is replaced by a short 
bladder-like organ, also set with more or less spatulate 
hair, suited for lapping, but not for getting down into 
deep flowers. Bees of this sort we find on our shallow 
flowers like those of the strawberry, blackberry and 
other Rosacea^, and many of these gather no honey at all. 

It is a delightful pastime, although not always easy, 
to investigate the domestic economy of the various 
bees. Some of them make nests or cells of mud gathered 
from road-side puddles; some bore into twigs, branches 
or even boards and in the tunnels so chewed out form 
the cells in which a brood is raised; some make cells of 
wax in cavities of trees; others seek a cavity under the 
turf, and in a mass of pollen raise their brood with little 
attempt at making cells of any kind; and yet others 
dig down deep underground, five or six feet below the 
surface a'nd, far from the light, build the homes in which 
their young are developed. And when we find a bee- 
home, we can always recognize it by the character of 
its store. It may be a cake of solid pollen, packed hard 
in a definite, loaf-like form, or it may be a semi-liquid 
mass of mixed pollen and honey, so arranged that the 
larva may feed on, without being imbedded in, it. But 
always there is pollen, and the pollen gatherer is always 
also a plant fructifier. 



30 



INSECTS 



There are many others among the Hymenoptera 
that are useful in the work of polHnation because of 
their habit of feeding among the flowers, even if not on 
them ; but all this is based on the same visits which the 
flower encourages and of which it takes advantage; 
but no account of this sort 
of relationship could be con- 
sidered even passably com- 
plete, without some reference 
to the complicated relation- 
ship existing between the 
Smyrna fig and the minute 
little Blastophaga, a species 
whose life relations have been 
beautifully worked out by the 
Entomologists of the United 
States Department of Agri- 
culture. 

The Smyrna fig of com- 
merce depends for its edible 
quality upon the ripened 
seeds that it contains. The 
fig is not really a true fruit 
as that term is generally 
defined, but is a thick fleshy 
envelope within which the 
flowers are contained. In 
the Smyrna fig these flowers 
are all female and no pollen is produced anywhere on 
the tree. Left to themselves, such trees could never 
produce ripe fruit, and that was the condition of the 
Smyrna fig orchards in CaUfornia; prior to 1900. In the 
Mediterranean countries, whence our commercial sup- 
ply is generally derived, there are found beside the culti- 
vated also several varieties of wild or caprifigs, which 




F1G.8.— a, cell of ^MgocWora with 
egg laid on pollen mass; b, cell of 
Andrenid with egg resting on mix- 
ture of pollen and honey; c, cells of 
carpenter bee in wood; d, mud cells 
of mason bee in burrow — c and d, 
after Packard. 



THEIR RELATION TO PLANTS 



31 



produce three crops of fruit during the season. These 
fruits contain male flowers, producing an abundance of 
pollen; but this pollen is never naturally discharged 
from the envelope containing the florets. 




Fig. p. — Blastophaga pollenizer of fig: a, female; b, c, male in two positions. 



Yet it was recognized by the fig-growers in the 
Orient that to obtain fruit of the commercial edible 
varieties, it was necessary to bring to them when in 
bloom, branches containing fruit of the caprifig, which 



32 INSECTS 

were usually hung up in the tree which it was intended 
to fructify. This work of pollination is accomplished 
by the Blastophaga already referred to, although, far 
from benefiting itself in the process, the insect dies 
without even being able to continue its kind. 

In the caprifigs the female flowers are replaced by 
little gall-like swellings in which the larvae of the Blasto- 
phaga develop. One generation of figs, the so-called 
"mammse," remain on the trees during the winter and 
by the time they are ready to drop, there is already on 
the trees a new or spring crop of fruit, known as the 
"profichi. " By the time that this crop is in proper 
condition, the insects that have hibernated in the 
"mammae," are fully developed, the wingless and almost 
blind male Blastophaga has fertilized the female before 
she is even out of her cell, and the latter, leaving the 
dried-up fig by the small anterior opening, makes its 
way into the new figs, to provide for a new generation. 
In the "profichi" this generation matures at the time 
the commercial Smyrna fig is in proper condition and 
the females, emerging pollen covered from the "pro- 
fichi," enter the small opening of this true female flower 
receptacle, if they find themselves in a tree bearing them. 
But in this Smyrna covering all the female florets are 
fully developed, and the gall-hke swellings that replace 
them in the caprifigs are absent. The insect therefore 
moves about over the entire interior surface of the 
pouch, seeking a place to oviposit, and in the process 
distributes its load of pollen everywhere. It event- 
ually dies without reproducing, and usually without 
even being able to make its way out again. But 
though the insect has lost its life, the tree has gained 
and the seed pouch that we know as the fig, comes to 
maturity and ripens seed. 



THEIR RELATION TO PLANTS 33 

At the same time that the Smyrna fig which produces 
the edible commercial fruit is in bloom, there is also 
another crop developing on the caprifigs, and these are 
known as "mammoni." The Blastophaga issuing from 
the "profichi" on the same tree, naturally enter these 
fruits which are of the same character as the preceding 
crops, and are able to continue their kind, coming to 
maturity when the third crop is ready for their reception. 
This third crop represents the "mammae" or over- 
wintering form, from which the "profichi" of the fol- 
lowing season are again entered by the Blastophaga. 

Here we have an extremely complicated relation- 
ship which, reduced to its simplest terms, means that 
in order to produce the commercial Smyrna fig there 
must be suitable caprifigs producing "profichi" infested 
by Blastophaga, at a period corresponding to the develop- 
ment of the female flower capsule. And as the insects 
are very small and very frail, the caprifigs must be 
either well distributed among the Smyrna trees, or the 
infested "profichi" must be gathered and distributed 
among the trees to be pollenized. 

The accounts, published by Dr. L. O. Howard in the 
Bulletins and Reports of the U. S. Department of 
Agriculture, make interesting reading and show how, 
after many trials and much painstaking investigation, 
the Blastophaga and the necessary caprifigs were finally 
introduced into the fig-growing districts of California, 
and how a new industry, absolutely depending for its 
continuance upon a minute hymenopterous insect, was 
finally established upon a firm and scientific basis. 

How many cases of this kind exist among plants 
having no present economic value it would be difficult 
to estimate, and how so complicated a relationship ever 
became established is not yet explainable even by a 
theory. 



34 INSECTS 

The Lepidoptera have been already incidentally 
referred to as pollenizers and they rank, as an order, 
next to the Hymenoptera in importance. Butterflies 
and moths, when they feed at all, feed only on liquids 
and most of them on prepared plant juices or nectar. 
The butterfly hovering over a flower and sipping honey, 
is a familiar figure, and the visits of hawk-moths to the 
flowers that open at dusk are fairly well known; but 
that busy life that stirs among the flowers after night 
falls, is unknown except to the naturalist who prowls 
about in wood and field, among the hedges and along 
the road, often with a bulls-eye lantern like a thief; 
seeking indeed to surprise some of nature's secrets by 
artificial light, his organs of sight being far inferior to 
those of the creatures whom he seeks to study. 

That many flowers are most fragrant at night, and 
that many fragrant, night-blooming flowers are white 
or without striking colors, is a commonplace to one 
who knows the country at all ; but that this penetrating 
fragrance is to attract insect visitors at a time when sight 
does not suffice for an invitation is not so well known. 
And yet it is at night that the most abundant, albeit 
almost noiseless, life can be observed on such flowers, 
and here we will find owlet and other moths busily 
engaged in probing every floret and incidentally accom- 
phshing nature's aim of reproduction. I say "inci- 
dentally" with intent in this case, because neither 
moth nor butterfly has any use for the pollen that it 
dislocates and relocates as it moves. It is after food, 
purely and simply, and that food is nectar: if in reaching 
that nectar the tongue, pollen laden, is brought into 
contact with the stigma, that is merely because the 
insect could not help itself, any more than it could pre- 
vent the adhesion of a few grains of pollen from 
another flower. 



THEIR RELATION TO PLANTS 



35 



Exceptions occur always and that of Promtba in its re- 
lation to Yucca has been related ; but in general the Lepi- 
doptera pollenize as a mere incident and with the tongue, 
while feeding. And this tongue is a really interesting bit 
of structure. It is coiled like a watch spring when at rest 
between the mouth feelers, and no one would suspect its 
presence or size from an ordinary dried specimen; but 
when uncoiled it is often as long and sometimes much 
longer than its bearer, and here 
again we have that beautiful 
ringed structure that adapts it- 
self to so many purposes among 
the insects. There is no flower 
so deep that its nectaries are 
beyond the reach of all insects 
but there are many flowers so 
deep that only a single long- 
tongued species is invited. And 
therefore we have an abun- 
dance of species with tongues 
of less than an inch in length, 
quite a number that have them 
from two to four inches and 
a very few where ten or even 
twelve inches are attained. 

The butterfly tongue really consists of two separate 
parts or halves, the modified maxillae, held together 
by specially developed structures; and the space be- 
tween them forms the tube through which the liquids 
are carried into the mouth. Each half contains its 
own supply of muscles, a large tracheal tube extends 
to the very end, and there is an excellent supply of 
nerve-fibres to guide the insect in its operations in the 
depths of the florets. 

Most of the tongue is bare or set with scanty stiff 




Fig. io. — a, tip of butterfly 
tongue showing the sensory pits 
and taste cups; 6, section through 
tongue showing division into two 
halves. 



36 INSECTS 

hair only; but at the tips in the different species, are 
found a great variety of tactile structures, taste cups 
and gathering processes, by means of which our moth 
not only recognizes the presence of something good to 
eat, but manages to get it all, as well. In the adult stage 
as moths or butterflies, the Lepidoptera have few bad 
and many good qualities; but in the larval or cater- 
pillar stage the reverse is the case. As pollenizers the 
Lepidoptera could be missed much more readily than the 
bees; none of our cultural plants depending upon 
them for their continued existence. 

Among the Coleoptera or beetles there are many 
that frequent flowers for one purpose or another and 
many of these are more or less pubescent or covered 
with hair, so that they may be and often really are 
much covered by pollen as they move about. And 
as they move about they do without question add 
their share to plant fruitfulncss; but they are also very 
often feeders upon them or upon the pollen. In so 
far as they are pollen-feeders merely, this does little 
harm, because that is usually produced in great ex- 
cess; but some feed on the pollen in such a way as to 
rob the plant of all possible chance of benefit. For 
instance the strawberry -weevil in the larval stage 
subsists altogether upon pollen. But the parent beetle 
punctures the unopened bud, lays the egg in the mass 
of forming pollen and then punctures the stalk below 
the bud, so that the latter may never open. This is 
sheer robbery without corresponding benefit and, on the 
whole, flowers pay pretty heavily for such incidental 
advantages as Lhey derive from the visits of beetles. In 
any case the pollination is purely incidental, for the 
beetles gather neither pollen nor honey, and the hairy 
covering is not modified to make it especially .serviceable 
as a carrier. 



THEIR RELATION TO PLANTS 



37 



Diptera or flies are often intimately associated 
with flowers, and many of these are hairy, some even 
with spurred or compound hair; but none with modi- 
fications that adapt them especially or peculiarly as 
pollenizers. We have one family, the BomhyliidcB or 
bee-flies, resembling bumble-bees somewhat in appear- 
ance and quite as hairy, many of which also have a 
long tongue rivalling some of the Lcpidoptera. But 
their habits are quite different. One 
never sees them buried in a flower 
or rolling about among the blos- 
soms, pollen-covered. On the con- 
trary they usually hover daintily over 
bare, sandy areas or, if over flowers, 
then very delicately and resting 
lightly when at all. That they are 
of some use to the plants is prob- 
able; but they have no important 
function. And the same is true of 
the SyrphidcB that are found so 
often resting on or about blooms: 

the majority of these are bare, or have only a thin soft 
vestiture and slender hairless legs to which pollen 
could not adhere if it would. 

An exception to this general statement is found in 
the chrysanthemum or "drone fly," a burly bustling 
species that becomes conspicuous late in the season 
and resembles in size, color and general appearance a 
honey bee, for which indeed it is often mistaken. A 
little experience, however, shows that it has no sting, 
and therefore the term " drone fly " is not so 
inappropriate. 

Growers of chrysanthemums believe this fly of 
great importance in the pollination of that plant and 
they may be correct; but on other plants or flowers 




Fig. II.— Chrysanthe- 
mum fly; Eristalis tenax. 



38 INSECTS 

they are of little use. Their habits in the early stages 
are about as unlike those of the adults as it is easily 
possible to imagine. The larvae live in all sorts of semi- 
liquid excrementitious matter and are known as rat- 
tailed maggots, because of the long anal process by 
means of which they obtain air from above the surface 
of the filthy mess in which they live. 

The number of flies known to us is already very 
great, and the number that still remains to be studied 
is probably even greater; while as to their habits we 
know them in the most general way only. There may, 
therefore, be groups more decidedly beneficial to 
plants than anything that I have mentioned; but 
there can be nothing comparable with the bees, since 
none of the flies store food for their progeny. 

The fact is, then, that many plants depend for their 
reproduction entirely upon insect visitors. Some flowers 
are so constructed that only very specialized forms can 
accomplish the function of pollination and there is in 
many such cases a mutual dependence: the insect can- 
not exist without the plant nor can the plant continue 
its kind without the insect. Other flowers issue a general 
invitation by bright colors, wide open parts, abundant 
pollen or filled nectaries, readily accessible to anything 
that may come along. Yet others depend upon nectaries 
that are attractive, but are so situated that any insect 
that succeeds in gaining access to them must of necessity 
pay in pollenizing. And here we come to a subject on 
which the botanist has his say, and shows how ingenious 
are some of these plant structures and how well adapted 
to their end, so that pollination may even be accom- 
plished without the necessity for bringing the pollen 
into contact with the insect at all, the latter merely 
releasing the trigger that restrains the distribution of 
the fructifying material. 



THEIR RELATION TO PLANTS 39 

There is one other method in which insects are 
useful to plants, and that is as food. A very few plants 
are "carnivorous" or feed upon animal food, and that 
animal food consists mostly of insects; but that is a 
relation which is extremely simple in character al- 
though the plant habit is exceptional. 



CHAPTER III 

THEIR RELATION TO PLANTS AS DESTROYERS 

While, as has just been shown, there is a mutual 
interdependence of plants and insects in which both 
may be benefited, or if one is harmed, the benefit 
derived is so far in excess of the injury suffered that it 
does not count against the value of the relation, there 
is also a kind of dependence in which the insect gets 
all the benefit, and the plant all the injury. 

A vast number of insects depend absolutely upon 
plants for their very life and give nothing at all in re- 
turn: they are destroyers pure and simple, using the 
plant tissue as food, as material to supply protection, 
or as a habitation. But the amount and character of 
the injury vary enormously and may either be a neg- 
ligible incident in the life of the plant, or form the 
principal check to its growth or cultivation. 

We may dismiss with no more than a mere mention 
that vast horde of insects that gets into plants when 
they are dead and begin to disintegrate. Nature dis- 
likes dead organic matter, and when a tree or plant 
is dead or dying, or when decay begins in a sappy fruit 
or fungus, there are insects among other agents ready 
to reduce it to that inorganic condition from which it 
originated. While the actual death of a diseased or 
weakened tree is often hastened by such insects, they 
can hardly be said to be enemies in the direct sense ; but 
scavengers, ever ready to begin their office and fostering 
the condition in which it becomes their legitimate prey. 

Beginning with the simplest order, the Thysanura, 
we find few plant destroyers among them. Originating 



THEIR RELATION TO PLANTS 41 

as they did in primitive times when dampness, mud 
and ooze were prevaihng conditions and vegetable 
life just established, they were fitted to live and gain 
their subsistence in disorganized tissue: they were 
simple forms of scavengers, and so they are to-day in 
most cases. They are always found where there is 
moist vegetable decay and sometimes, in manure beds, 
they occur in countless numbers. In fermenting sap, 
under bark of trees undergoing moist decay, in masses 
of leaves and similar localities, these species may gen- 
erally be sought. Their direct influence upon growing 
vegetation is extremely small. 

In the Neuroptera there has been an advance, al- 
though, as these were also primitive species and largely 
adapted to aquatic or semi-aquatic life, the vegetable 
feeders are in the minority. Almost everywhere the 
larval life is more or less predatory in tendency and 
in some, hke the Odonata or dragon flies, this predatory 
character is carried into the adult stage. The feeders 
on vegetable matter, like Psocids and Termites, usually 
attack dry or dead tissue or feed upon Lichens and 
similar material. None of them rank as destroyers of 
the higher forms of plant life, although Termites do in 
some instances attack growing vegetation. 

In the Hemiptera we have a well-developed series 
of terrestrial species, the vast majority of which are 
feeders on plant life or on plant juices drawn from 
living plants. The mouth structure of the insects is 
such that they can feed only on the liquid which they 
draw from a punctured tissue, whether vegetable or 
animal, and therefore, primarily, the injury is due to 
a withdrawal of sap, severe in proportion to the amount 
of liquid thus withdrawn. Secondarily, injury is caused 
by an interruption of the circulation in the plant, due 
to a hardening of the exhausted tissue, or the drying 



42 



INSECTS 



out of the cells from which the liquid matter has been 
abstracted. More rarely a positive poisoning of the 
tissue occurs, due apparently to the injection into it 
of the salivary secretion of the insect, and this may 
result in the death of all that portion of the plant be- 
yond the puncture. That sort of injury is often pro- 




FiG. 12. — Mouth parts of a plant louse — a, the jointed beak; b. the 
lancets; c, the feeler; d, the foot. 



duced on succulent plants like the Cucurbs, including 
cucumbers, melons and the like, or Solanacea, includ- 
ing potatoes, tomatoes, egg-plants, etc., the offenders 
being mostly plant bugs of the families Capsidce, Lyg- 
(EidcB or CoreidcB. 

Plant Hce are universally distributed and there is 
scarcely a plant not in some way subject to their attacks. 



THEIR RELATION TO PLANTS 43 

They are insignificant as individuals; but dangerous 
in hosts: and hosts grow out of individuals in an in- 
credibly short time, owing to their fecundity. Given 
a few eggs on the tip of an apple twig in winter, they 
hatch into young lice as soon as the leaf-buds open 
and, in a week or ten days, depending upon weather 
conditions, these begin to bear living young. All the 
specimens hatching from the winter eggs are parthen- 
ogenetic females; i.e., females which do not require 
to be mated with a male before reproducing their kind; 
and, when once reproduction begins, it is in the nature 
of a continuous performance; four, six, eight or more 
young being produced in a day and for several days in 
succession. Long before this stem-mother has reached 
her limit of increase, the first-born daughters, partheno- 
genetic like herself, have in turn begun the task of 
multiplication so that, by the time the leaves are fully 
formed, the surfaces are covered by plant lice, and in- 
stead of unfolding and reaching full size, they are 
curled, twisted and crippled, forming an unsightly 
mass instead of a beautifully unfolded cluster or tuft. 
And now we are apt to get a secondary efifect due to 
a peculiarity in feeding. Not content with absorbing 
only enough to sustain life and to reproduce, the insects 
gorge continuously and, when incapable of containing 
more, they eject through the anus a stream of a clear 
sweetish liquid, known as honey-dew. It was cur- 
rently believed that the two tube-like structures near 
the end of the abdomen were the chief organs through 
which this honey-dew is excreted and they are there- 
fore popularly known as "honey-tubes": more technic- 
ally they are termed cornicles, which conveys no opinion 
as to their function. This honey-dew drops upon the 
leaves below, often in such abundance as to form a 
complete coating and that, in turn, is an excellent 



44 



INSECTS 



culture medium for a soot fungus which forms a black 
covering that disfigures if it does not kill the foliage or 
fruit. It goes without saying that what is true of the 
apple, which I have chosen for an illustration, is equally 
true of the cherry, the maple, the orange, lemon or any 
other tree or plant subject to the attacks of plant lice or 
others of their allies also producing honey-dew — mealy 
bugs, white-fly, Psyllids and even some scales. 




apple louse: b, stem-mother; a, winged parthenogenetic form; 
C, adult male; d. winter eggs on twig. 



To return, however, to our stem-mother on the 
apple, whom we left engaged in the task of increasing 
her kind. She was bom without wings and never 
acquires them, and her daughters are like her in this 
respect. But after the second generation matters 
become crowded, and unless relief is somehow obtained 
there will be more than can be maintained on the orig- 
inal tree. And so in the third and later generations a 



THEIR RELATION TO PLANTS 45 

variable number of individuals develops further and 
becomes winged. There is not in this case any genera- 
tion in which all the individuals are winged, although 
there are species in which such a condition exists. It 
is simply that out of a dozen individuals born of the 
same mother on the same day, a number develop 
wings and fly away to other trees or plants. They are 
no further advanced, sexually, than the stem-mother 
and when they reach their new homes they also pro- 
duce living young, which may become winged or re- 
main wingless; and this sort of reproduction continues 
until the end of the season and the gradual decrease 
of sap in the trees and plants forces a provision for 
winter rest. Late in the fall, therefore, a generation is 
produced in which both sexes are represented and 
from a union of these the winter egg is produced. 

Now while this in a way epitomizes the usual his- 
tory of plant lice, there is an infinite amount of varia- 
tion. A species that is confined to one tree or similar 
food plant may do very well without much modifica- 
tion; but a species which feeds during the summer on 
a plant that dies down completely before winter, needs 
some provision that enables it to continue its kind 
elsewhere; hence we have migrations in early summer 
from and in late fall to the winter host. In a melon 
field, for instance, there may not be a plant louse until 
the vines are well developed: then on some warm, 
almost windless day in June, the air will be found full 
of drifting, winged aphids and next day a sprinkling 
of them may be noted all over the melons, giving rise 
to the summer generations which, in late fall, again 
produce return migrants that find their way to plants 
upon which they can pass the winter. Sometimes 
there seems to be a direct relationship between two 
plants, as apple and wheat for one form of Aphid that 



46 INSECTS 

attacks both, or between the plum and the hop, where 
the insect cannot exist unless both its alternate hosts 
are present. At other times, as in the case of the melon- 
louse, the insect has a variety of food plants and the 
migration is not essential to the continuance of the 
species. In fact it is not even necessary for all plant 
lice to go into the egg stage, for some species winter as 
parthenogenetic females on plant remnants or on stools 
like the rosettes of cruciferous plants. In tropical coun- 
tries the resting stage is often during the dry season, 
when vegetation has little spare moisture. 

Some species attack only the roots of plants, and 
these are usually wingless, and often without honey- 
tubes or cornicles. Some inhabit the roots at one 
season and the leaves at another, the winter being 
usually spent underground, while a large part of the 
growing period may be passed on the foliage, the spread 
of the species being provided for there. Such species 
may be very little modified, like the black species that 
occurs on peach, or very greatly specialized like the 
Phylloxera that occurs on grape, and is so great a 
factor in all countries where the vine forms an impor- 
tant part of the agricultural product. This Phylloxera 
vastatrix winters on the roots as a partly grown, wing- 
less form. It grows rapidly in spring and lays eggs, 
the young from which are, like their mothers, wingless 
and parthenogenetic, laying eggs and producing others 
like them in turn throughout the season, always from 
unfertilized eggs. In most localities, about midsummer, 
some specimens acquire wings, work their way to the 
surface and fly to other vines, thus providing for the 
rapid spread of the species. These winged forms lay 
from three to eight eggs on the leaves, some of them 
large, producing females, the others small, producing 
males. These sexed forms seem to be produced only 



THEIR RELATION TO PLANTS 



47 



for the purpose of renewing the vitahty of the species 
for they are without wings, incapable of flight and with- 
out mouth parts, incapable of feeding. They are 




Fig. 14. — Phylloxera vastatrix — a. sound grape rootlets; b. rootlets with newly 
formed galls; c, same with old, dried up tissue; dd, groups of lice on roots and 
rootlets; e. f, female pupa, above and beneath; g. h. winged females; i, antenna; 
J, oviparous wingless female and her eggs; k. root showing location of the eggs. 



sexually mature when born, copulate soon afterward, 
and each female produces one egg which hatches into 
a form similar to that which started the cycle in spring. 
But the winged form is not essential for this renewal. 



48 INvSECTS 

for at any time during the summer the underground 
forms may lay eggs of two sizes producing similar sexed 
forms that act precisely as did those above ground. 
So, some of the parthenogenetic forms may leave the 
roots and crawl up the stem to the foliage, where their 
progeny form those characteristic galls which strike ter- 
ror into the heart of the European viticulturist, while 
they are frequently not even recognized by the vine- 
grower of the eastern United States. Nor is this leaf- 
form a necessary feature in the cycle and it does not 
occur in all localities, so that outward indications of 
Phylloxera infestation may be completely lacking ex- 
cept in the condition of the vine. The Phylloxera are 
gall-makers as a rule, and on the roots of grape pro- 
duce swellings and distortions which, on vines not 
accustomed to them, result in the death of the roots 
or serious disturbance in function, so that the vines 
sicken and may die. In the original home of the species 
in eastern North America no especial injury is caused; 
on the Pacific Coast injury may be severe, but the 
insect does not spread readily, and so its march may 
be checked; while in European countries the native 
vines succumb very easily to the attack of the insect 
and its spread is rapid where energetic measures for 
its destruction are not resorted to. 

There are other species of plant lice producing galls: 
some on hickory make bladder-like structures of con- 
siderable size, and others produce ridges aptly com- 
pared to a cock's comb, on elm. In fact, from the 
simple distortion produced by a feeding along the veins 
on the under side, to characteristic bladder-like struct- 
ures, every sort of intermediate form exists, and as 
a rule these produce no very serious results on the 
plant. It is astonishing how great a number of such 
insects a plant may support without interfering with 



THEIR RELATION TO PLANTS 49 

its power to maintain life and reproduce its kind; which 
be it noted, is quite a different matter from an injury 
which will make the plant unprofitable to the farmer 
or fruit-grower. 

Scale insects are close alhes of plant lice in many 
ways and yet totally different in "many others. The 
popular name is derived from the fact that most of the 
species have the appearance of a fragment or scale of 
tissue plastered upon or against the ' bark or foliage 
of the plant attacked. And so we have soft scales and 
armored scales, which differ radically from each other. 
In the soft scales, so named because the outer covering 
is usually waxy in texture, the outer covering or scale 
is part of the insect itself, not separable from it in any 
way, and the term, scale insect, is strictly correct. In 
the armored scales, on the other hand, the scale or 
covering mass is tougher, more parchment-like, and 
forms no part of the insect, although produced or ex- 
creted by it. It is possible, therefore, to lift the scale 
without in any way interfering with the creature be- 
neath it; the covering being formed in part by the 
cast skin of the insect and in part by a fibrous excre- 
tion from special glands. 

Scale insects, like plant lice, are capable of enormous 
feats in the reproductive line, one thousand million de- 
scendants for a single pair, during a single season, 
having been figured out for one of the species! Thus, 
given a scale introduced without natural checks into 
a region where conditions favor it, and the effect upon 
its host-plant can be readily imagined. The practical 
experience of the Pacific Coast with the cottony cushion 
scale on citrus fruits, and of the Atlantic Coast with 
the San Jose scale, are recent instances that illustrate 
the destructive powders of scales; the first a soft, the 
latter an armored form. 
4 



50 INSECTS 

Scale insects feed on the juices of their host as do 
the plant lice, differing in the fact that they are more 
or less fixed to a single spot on the plant: absolutely 
fixed in the armored scales, with a very limited range 
of motion during a part of their life in the soft scales; 
the latter being in some cases not far removed from the 
mealy bugs which are active throughout their life and 
produce a powdery material that does not form a com- 
plete covering. Some produce living young and breed 
throughout the season, like the San Jose scale; others 
are oviparous and have only one distinct brood, like the 
cottony maple scale. In some there are only a few 
eggs, in others they are almost uncountable, and thus 
there is a great range in the life cycle, although the 
nature of the injury done is always the same. 

One characteristic feature is the difference between 
the sexes. The males, throughout the CoccidcB, are 
very minute, frail, two-winged creatures without func- 
tional mouth parts and two pairs of eyes; one pair 
replacing the lost feeding organs. These males are 
often furnished with long anal styles or filaments, and 
their only function is to fecundate the female. The 
latter feeds throughout life, never becomes winged, and 
her dead body often serves as a cover or shelter for the 
egg mass that she produces. 

The injury caused is primarily due to the abstrac- 
tion of sap; but quite a number of species produce a 
distinct poisoning of the bast or bark tissue, often 
evidenced by a red or purplish discoloration. Where 
this occurs the twig or branch dies sooner or later. 
Sometimes pits or depressions are formed where a 
little group of scales is lodged and, in fact, there are 
infinite variations in the character of the injury, due 
to the peculiarities of the plant attacked and to the 
method of feeding by the insects. Some of the soft 



THEIR RELATION TO PLANTS 



SI 




Pic 15 —Development of the San Jose scale: a. larva; b. its antenna; c. 
female with young showing through body wall; d. outlme of anal plate; e, male 
adult. 



52 INSECTS 

scales produce honey-dew in great quantity, and the 
resulting soot fungus does almost as much injury as 
the insect. In the olive and citrus groves of the Pacific 
Coast, trees infested by the black scale are often recog- 
nizable as far as they can be clearly seen, and discolora- 
tion of fruit is a distinct element of the injury caused. 

Quite a number of others among the allies of scales 
and plant lice produce honey-dew and its consequences, 
and there is a long series of species, including the leaf- 
hoppers, tree-hoppers and others of the Homopterous 
section, that cause more or less injury to their food 
plants by the direct robbery of the vital juice or sap; 
but there are none differing so greatly from the methods 
of plant lice and scale insects as to require special 
attention here. 

A somewhat different type of injury is caused by 
some tree-hoppers and Cicadas or harvest flies. These 
do little or no harm by direct feeding; but utilize the 
twigs and branches of the plants on which they live 
as places of deposit for their eggs in such a way as to 
kill or severely cripple them. Some of the tree-hoppers 
cut little slits in the twigs to receive their eggs, and 
these slits never heal. The tendency is rather to an 
enlargement of the scar which permanently weakens the 
shoot and sooner or later causes a break. The chief 
sinner in this direction is the periodical Cicada, better 
known as the "17-year locust," and wherever and 
whenever that makes its appearance in numbers, the 
tips of the forest trees in early fall show brown ends 
as if a fire had passed over them. In such forests it 
means only a moderate pruning and no real injury to 
the trees; but in orchards, especially of young trees, 
injury is often severe, weakening the shoots and branches 
so that they break under a load of fruit. And these 
punctures also refuse to heal, and remain permanent 



THEIR RELATION TO PLANTS 



53 



sources of weakness, apt to result in a break at any 
time. I would never advise planting a nursery tree 
whose trunk had been used by Cicadas for ovipositing. 
In the Heteropterous series the species are usually 
larger; but the life histories are simpler and the injury 
is not materiallv different. Here, among the plant 




Fig. i6. — a, Ccresa bubalas, a tree-hopper, ovipositing in slits b\ the eggs, d, 
arranged as at c; old scarred punctures at e. 



bugs, the poisoning effect already referred to is often 
noticeable, and is frequently of more importance than 
the exhaustion caused by the direct feeding. The 
chinch-bug may serve as the best known example of 
the destruction causable by these species and of the 
results that come only from the enormous numbers 
in which they feed. There is nothing here but a direct 
loss of vitality due to the abstraction of the plant juices. 



54 INSECTS 

The order Orthoptera, as a whole, consists of plant 
feeders: from the earwigs to the crickets there are 
only a few groups where vegetation is not the chief 
or only food. The earwigs are curious because of 
their resemblance to beetles and their large anal for- 
ceps, and they feed largely in, though not always on 
flowers. Not many occur in North America and their 
chief interest lies in the fact that the female broods 
over her eggs after they are laid: an altogether unusual 
character in this series of species. The roaches are 
not normally troublesome to growing vegetation and 
are of most interest as household pests, where more 
is said of them. The Mantidce or graspers is the 
only group of distinctively predatory species in the 
order and they are very few in number. The PhasmidcB 
or "walking sticks" are devourers of plant tissue, 
interesting because of their resemblance to the twigs 
and leaves among which they live, and because of 
their habit of dropping their eggs to the ground with- 
out care as to their location and future ; as far removed 
as possible from the habit of the earwigs. Their injury 
to the plants is of the simplest possible description 
and confined to a partial destruction of foliage, which 
means little or nothing to the plant. 

The grasshoppers, on the other hand, are among 
the best known of plant destroyers. Under the name 
"locusts" their ravages have been written of in the 
Bible and by later writers on conditions in Africa and 
the Mediterranean countries. The migratory locust 
has thus come to represent the very type of destruc- 
tive invasion, and the Rocky Mountain locust or grass- 
hopper in our own country is not less well and unfavor- 
ably known for its injuries. 

The short-horned grasshoppers, which are the 
species now under consideration, quite usually lay 



THEIR RELATION TO PLANTS 55 

their eggs in little masses in holes in the ground, which 
they bore with the homy valves at the end of the 
body, and they select moderately firm, dry ground for 
that purpose. Much moisture is dangerous or even 
fatal to the eggs, hence it is in desert or semi-arid 
countries that they are most abundant. Such condi- 
tions in our country exist among the foot-hills of the 
Rocky Mountains and no place that I have ever seen 
exceeds that region in the variety and abundance of 
its grasshoppers in a normal season. Sometimes, 
when conditions become unusually favorable, grass- 




FlG. 17. — The American grasshopper or locust, Schistoccrca americana. 

hoppers may become so very abundant that the vege- 
tation in their native locality is insufficient to support 
them, and then some species better fitted for flight 
than others, take wing and seek new feeding grounds. 
Some are unable to get very far, and rest as close to 
home as they can, starving if they get beyond the limits 
of their strength without discovering new pastures; 
but other, longer winged species, accomplish hundreds 
of miles from the Rocky Mountains to the Mississippi 
Valley, alighting first where cultivated lands begin. 
Thus Kansas, Nebraska and the Dakotas were pre- 
eminently sufferers from grasshopper invasions, and 
not infrequently conditions were sufficiently good 
there to permit the insects to lay their eggs, providing 
for a brood which the year following destroyed the 



56 INSECTS 

vegetation while still unfledged, and then migrated 
yet further east to do destructive work as adults and 
to perish gradually, in the egg stage, in the moist un- 
suitable soil. No one who has not seen grasshoppers 
in this western country can form any real idea of their 
actual abundance, and their destructiveness has been 
the theme of many a writer. They eat any green thing 
if they must; but favor the low plants of field and 
meadow so long as they last. 

Conditions now are much better than they were 
and can never again be quite as bad. A large area of 
what was at one time ideal breeding ground, is now 
irrigated and under cultivation, and the enormous 
belt of alfalfa and other crops now basing the foot- 
hills, checks and takes up the migrating hordes that 
occasionally start from the uncultivated areas. The 
march of advancing cultivation spells the doom of 
some of these grasshopper species, as it has that of 
many another animal; but meanwhile the grass- 
hopper is putting up a good fight and is still causing 
trouble. 

While there is considerable variation in grasshopper 
habits and life history, some of them laying their eggs 
in soft or decaying wood tissue, there is little in the 
character of the injury caused; it is always a direct 
eating of the plant, rarely threatening its life, however 
much it may be injured for agricultural purposes. 

The long-homed or meadow grasshoppers are most 
abundant in the places shunned by the short-homed 
species. They delight in moist meadows, in reedy 
open swamps, and are abundant in the marshes along 
the sea and lake coasts. They are usually of some shade 
of green in color, and have a more or less well marked 
blade-like ovipositor, by means of which they lay their 
eggs in the stems or leaves of the grasses and other 



THEIR RELATION TO PLANTS 57 

vegetation among which they Uve. The_y are largely 
seed feeders when seeds are to be obtained, but eat 
grassy tissue as well. A character of interest is found 
at the base of the wings in the males, where the over- 
lapping parts are ridged and toughened to form a 
stridulating or musical apparatus of a very effective 
order. The best known among this type are the Katy- 
.dids, which are often tree and shrub dwellers but do 
not differ markedly in other respects from the more 
lowly meadow inhabitants. 



Fig. 18. — A long-horned grasshopper, Microcentrum sp. 

The crickets are very diverse in their habits, both 
as to dwelling places and as to food; some confined to 
vegetable matter only, a few omnivorous and the tree 
crickets carnivorous. The latter are really the only 
injurious forms for, while they eat plant lice and similar 
creatures, they lay their eggs in the shoots of plants 
and sometimes cause their death; but this is an in- 
significant item as against their usefulness from the 
farmer's point of view. 

On the whole, while the order Orthopiera contains 
many plant destroyers, the destruction is rarely total: 
that is, it is confined to defoliation which does not 
threaten the actual life of the plant, however completely 
it may destroy its value agriculturally. 



58 INSECTS 

In the order Coleoptcra or beetles we have a very 
large number of species and a very great diversity of 
habits. They live under almost every conceivable 
condition where insect life is possible at all, and there 
is no organic matter, living or dead, which is not eaten 
by some Coleopteron in either the adult or larval stage. 
We may therefore expect to and do find enemies to all 
sorts of plant life and there is no part, from the tip of 
the finest rootlet to the topmost leaf, that is exempt. 

Just how it happened that certain types of struct- 
ure became associated with certain feeding habits 
makes a very interesting question on which there are 
widely divergent opinions; but for our purpose we can 
simply accept the fact that the general life habits of 
any beetle can be approximately stated from an ex- 
amination of the feet, the antennae or feelers and the 
general type of mouth. There are exceptions in every 
large group as the result of special adaptation, but for 
general purposes the test answers well. 

We have a large series of species, most of them 
terrestrial but a few aquatic, in which the antennae 
are slender, made up of usually eleven joints of similar 
form, and the feet are 5 -jointed on all legs. All these 
are predatory in general habits, both as larvae and 
adults, and none are characteristically enemies of plant 
life. There are some that eat plants, and a few have 
caused injury at times; but these are exceptional 
instances. 

Coming next in the order of series are the Clavicorns 
in which the antennae are thickened toward the tip so 
as to form a distinct enlargement or club: the feet, all 
of them with the same number of joints, though the 
number may be from three to five, none of them with 
the third joint lobed. By far the largest part of this 
series are scavengers, living in fermenting, dry or de- 



THEIR RELATION TO PLANTS 



59 



caying animal and vegetable material of all kinds. 
A very few, comparatively, are predatory and yet a 
smaller number are feeders upon living vegetation; 
none of them in any very characteristic way nor so as 
to threaten the existence of the plant attacked; but 
still giving variety to the series. 

These are followed by the Serricornia, in which the 
antennae have the joints more or less trigonate, or 




-Antennal structure of Colcoptera. a, filiform; b, clavate; c, serrate; 
d, lamellate; e, moniliform. 



saw-toothed, and the feet 5-jointed as a rule; always 
with the same number on all feet. Among these the 
vast majority are vegetable feeders, but this vegeta- 
tion may be dead or alive, and most of the feeding is 
on woody tissue rather than foliage. The " click beetles, " 
"snapping Ijcetles" or Elatcridcc are characteristic 
members of this series, and as wire- worms their larvs 
are ver\' often feeders on root tissue. The beetles gain 
their common names by the loose-jointed structure 



6o 



INSECTS 



between the prothorax and the rest of the body, and 
their habit of snapping or springing up with a jerk 
when turned on their backs. The wire-worms gain 
their name from the tough leathery texture combined 
with a slender wormlike form and most of them feed 
underground, devouring the roots of many sorts of 
plants, severely injuring or actually destroying such 
as they attack. But there is also a large contingent 
that lives in woody tissue — nearly always dead tissue 
and quite generally such as is well advanced in decay. 
The insects can scarcely be 
called borers, because they are 
hardly fitted to make their way 
in sound wood ; but in logs and 
stumps or even dead standing 
trunks they are often found in 
goodly numbers. 

Typical wood-borers are 
found among the BuprestidcB, 
which are usually metallic, hard- 
shelled beetles, generally of good 
size, often with handsomely sculptured wing-covers. In 
the larval stage these are known as flat-headed borers 
or "hammer-heads" because, immediately behind the 
mouth structures the first thoracic segment is much en- 
larged and often chitinized, giving the appearance of a 
very broad, flattened head, followed by a long slender 
body in which all the joints are well marked. These bor- 
ers work in the bast and sap-wood of the trunks and 
branches of trees and shrubs, making shallow galleries of 
more or less characteristic shape and sometimes enor- 
mous length. A single borer not over an inch and a 
quarter long, may make a gallery an eighth of an inch 
wide and over ten feet in length, leaving a trail of dead 
tissue that the tree in many cases cannot replace or mend. 




Fig. 20.— Click-beetle and wire 
worm from side and top. 



THEIR RELATION TO PLANTS 



6i 



If this trail is along or with the grain, not much harm is 
done; but in many cases it tends to a girdling or to a 
cutting across the grain that involves a large part of the 
circumference. And when there are several such borers 
at work in one tree, fatal results follow. I have seen 
entire orchards of pear trees and fields of blackberry 
killed by borers of this character. 

Sometimes, the larva, instead of making a long 
narrow gallery, eats out an irregular chamber beneath 





Fig. 2 1. — Flat-head apple borer: a, 
larva; b, pupa; d, adult. 



'. — .A.n irregular gallery made 
by a flat-head borer. 



the bark, and that sort of injury is not nearly so serious, 
since it does not so much interrupt the circulation of 
sap. So there is quite a little difference of habit in the 
selection of the tree to be attacked. Some species 
never enter living trees and these are, perhaps, in the 
majority ; but some never attack other than healthy 
tissue. As a rule, if trees are found infested by flat- 
headed borers, it can be assumed that they were al- 
ready in rather poor condition before the entry ; this 
new attack marking the first step in nature's attempt 
to get rid of an organism no longer aggressively healthy. 



62 



INSECTS 



In those species that attack dead tissue only, some 
of which, Uke the cigarette beetle and death watch, 
are treated in Chapter X, we get an approach to the 
scavenger type; and yet the term scavenger seems 
scarcely a fitting one since the material attacked is 
not in a condition of either ferment or active decay. 

In the "soldier beetles" and "fireflies," which by 
the form of their antennae are members of this series, 




Fig. 23. — May beetle: i, pupa in earthen cell; 2, larva or white grub; 
3,4. beetle from side and above. 



we have a wide departure from the general feeding 
habit, most of them being predatory in the larval 
stage, and feeders among flowers, where they feed at 
all, as adults. 

The series LameUicornia, containing species with 
the feet 5 -jointed and the antennae terminated by a 
leaf-Uke club, includes vegetable feeders almost ex- 
clusively, in both larval and adult stages, and, in gen- 
eral, the feeding is upon live vegetation. There are 



THEIR RELATION TO PLANTS 



63 



tissue which 
In the larval 



the usual exceptions of course, but really very few in 
number. The common "May-beetle" or "June-bug" 
may be selected as a good type and this, as an adult, 
exemplifies the habits of the series in its voracious 
feeding. Most of the beetles of this series feed in the 
adult stage, and in almost all instances it is a direct 
straightforward devouring of growing 
does not endanger the life of the plant, 
stage the species are known 
as white-grubs and in this they 
are much more dangerous since 
they feed upon the roots, often 
destroying the smaller plants 
such as grasses, berries and the 
like. The step from living to 
dead vegetable matter is a very 
short one and so we find here 
also quite a number of feeders 
on dead or even decaying 
plants, which of course are not 
among the direct plant enemies. 
In that great series of Phy- 
tophaga, which contains the 
families Chrysomclidce or plant 

beetles, and Cerambycida; or long-horned beetles, we find 
all the tarsi or feet apparently 4-jointed, the third joint 
lobed or divided into distinct parts. This is a very char- 
acteristic structure and almost always indicates a leaf- 
feeder. Most of the adult beetles in the Chrysomelidae 
feed very simply and openly on leaf tissue, devouring 
without plan or aim except to get enough. Occasionally 
we do get some characteristic bit of feeding like that 
of some flea beetles which eat little round holes, or 
make channels that render their work readily identi- 
fiable. The larvae vary more in their habits and, while 




Fig. 24. — Tarsi of Coleoptcra: 
a, normally 5 - jointed ; b, 4- 
jointed;c, 4-jointed with 3rd joint 
lobed; d, same from side: c & d 
always indicate a plant-feeder. 



64 INSECTS 

the vast majority are soft, naked, slug-like creatures, 
similar to those of the potato beetle, or only scantily 
clothed like those of the elm leaf beetle, there are some 
that are more slender, white, and worm-Hke, mining 
in stems, leaves or even roots, and making more or 
less characteristic galleries, channels or chambers. 
They may be only surface channels like those made 
on cucurbs by certain species of Diabrotica; they may 
be real borings like those made in root tissue by some 
flea beetles; or they may be mines in leaf tissue, like 
those made by some of the species of Hispids. It is 
rare that the attack of a ChrysomeHd really threatens 
the life of a plant, though there are exceptions to this; 
the grape-vine root- worm for instance, and other 
root-feeders. 

In the long-horned beetles, or CenimbycidcB, the 
adults do very Httle feeding; but the larvee are borers 
in woody tissue or in stems of plants, dififering from 
those of the Buprestids by being more cylindrical 
and with a less prominently dilated anterior portion. 
They are known as round-headed borers as distin- 
guished from the flat-headed kind already described, 
and their galleries in section are nearly round instead 
of transversely oval. As a rule, also, they are more gen- 
erally borers in heart-wood and do not make the irreg- 
ular shallow galleries under bark that are so char- 
acteristic of the flat-headed types. There is no part 
of a tree that is exempt from their attacks: from the 
roots to the very tips of the twigs it may be in- 
fested, and they do not confine themselves to sick or 
dying trees either: a perfectly sound tree is just as 
Hkely to be attacked as any other and, indeed, some 
species are found in sound trees only. There are many 
interesting points connected with the development 
of these borers, the life period of some of them being 



THEIR RELATION TO PLANTS 



65 



drawn out enormously under unfavorable conditions. 
Thus, if a piece of infested timber is worked up into 
furniture, a larva which normally matures in two or 
three years may live for eight or ten years or even 
longer; and in some cases wainscoting has been found 
infested, several years after it has been in place, var- 
nished and polished so as to forbid the idea that some 
misguided adult oviposited there after the boards 




Fig. 25.— Round- head apple borer: a. puncture where egg is laid; b. same 
in section; e, hole from which beetle has issued; /, same in section; g, pupa. 



were in position. Some species require the wood in 
a particular condition to secure their best development, 
and so a beetle, before laying its egg, may girdle the 
twig so as to interrupt the flow of sap and then oviposit 
above the girdled point. Other larvae bore into live 
twigs and, when ready to transform to the pupal stage, 
cut through from the inside until only the bark and a 
mere shred of woody tissue remain. Then the burrow 
is securely plugged with sawdust and the larva retreats 
S 



66 INSECTS 

into its gallery, above the point of cincture, certain 
that the next high wind will bring it safely to the ground. 
Considering the enormous variety of species and the 
number of points attacked, it is surprising that the 
amount of injury caused is not much greater than it 
is. But, aside from the natural checks, the insects 
grow slowly in the larval stage and are rarely great 
eaters; the borings of some of them being surprisingly 
short, considering the size of the larva and the length 
of time it feeds; furthermore, the twig and branch 
borers in most cases produce only a more or less in- 
judicious pruning, while the 
borings in the heart wood 
on a large tree do not neces- 
sarily threaten its existence. 
Still, these round-headed 
borers may be accounted 
among the more serious 
enemies of woody plants. 

Fig. 26. — Bean-weevil, natural A little offshoot from the 

size and enlarged, and a much in- 1 , r 1 • 1 ,1 .1 

fested bean. plant-tecdmg beetles are the 

BruchidcB, commonly known 
as bean- and pea-weevils because the majority of them 
attack the seeds of plants belonging to the Leguminosce 
or pod-bearing family. This includes not only the bean 
and pea of the garden, but such tree forms as the locusts, 
and almost every series has its own species of Bruchid 
that lives and comes to maturity in the seeds. The term 
weevil is not strictly applicable to these insects for, al- 
though the head is very small and pointed, it is not pro- 
duced into a snout, and the body is unusually obese, the 
wing-covers squarely cut off behind and leaving a large 
area of abdomen exposed posteriorly. 

Next comes a series known as the Heteromera, in 
which the anterior and middle feet have five joints 




THEIR RELATION TO PLANTS 67 

but the posterior four joints only. It includes a great 
variety of species, many of tlicm of sombre, uniform 
color, shunning the light, living in concealment and 
often or even generally feeding on dead or dry vege- 
table matter. Yet there are exceptions to this, as for 
instance the blister beetles which, in the larval stage, 
are semiparasitic, and as adults feed ravenously on 
vegetation. When they are feeders on living plants, 
however, it is as straight-forward devourers of leaf 
tissue that they appear, and they do not threaten the 
existence of the plant attacked, however much they 
may injure it for the farmer's purpose. 

And now we get the Rhynchophora or snout beetles 
which, broadly speaking, include the bark beetles or 
Scolytids and with them some of the most dangerous 
enemies to plant life. Popularly most of these species 
are known as weevils and, so far as I am aware, all of 
them are plant feeders. And there is no part of the 
plant from root to tip that is not attacked; no 
stage from seed to pollen that is not eaten by them. 
They are among the oldest of the Coleoptera in the 
geologic record and have adapted themselves to life 
on vegetation under all sorts of conditions. The term 
snout beetles calls attention to one of the most prom- 
inent external structures — the elongated head drawn 
out into a beak of varying length, at the end of which 
the small mouth parts are situated. For feeding pur- 
poses these do not seem to be especially well designed, 
indeed in many species the mandibles are deciduous 
and are shed soon after the adult is developed; but 
for hiding and placing the eggs no better nor more 
practical tool can be imagined. For instance, almost 
every one that has gathered nuts has had the experi- 
ence of finding some of them wormy, with absolutely 
no trace of an opening on the outside to show how 



68 



INSECTS 



that worm or grub ever got into it. If the grub is bred 
to maturity it will develop into a snout beetle with a 
very slender brown beak, from one half to three quarters 
of an inch in length or even longer. With this long 
snout the parent punctures the forming burr of the 
chestnut or husk of the other nuts, and into the very 
centre it runs its minute channel. It then turns, places 
an egg into the mouth of the opening so made and 
again turning, slowly and gradually forces the egg into 
place with the beak. The rapidly growing plant tissue 
effaces all trace of this puncture, and there we have 




Fig. 27. — A nut- weevil: B alani mis sp.: a, from above; 6, from side; c, larva. 



our embyro grub already in place, almost before there 
is any differentiation between shell and kernel. It is 
interesting to note in this connection how carefully 
nature guards against the extinction of any of her 
creatures by a season of adverse conditions. A species 
dependent upon the hickory-nut for instance might, 
in case of a total failure of that crop for some one year, 
become locally exterminated if all specimens followed 
the same routine. But were we to put loo grubs into 
confinement in fall, when nuts are ripe, and permit 
them to go underground to pupate, we would probably 
get not over sixty adults the spring following; and if 



THEIR RELATION TO PLANTS 69 

we left our specimens undisturbed we would probably 
get thirty more the next year thereafter and the re- 
mainder the third year following. This seems to be 
rather a wide-spread provision for tiding insects over 
a bad season and, not only in the snout beetles but in 
many other groups, single-brooded species that pass 
the winter in the pupal stage, may lie over for one 
or even two vears after the bulk of the brood has 
become adult. 

By virtue of this provision for placing eggs, many 
of the snout-beetle larvae are feeders in blossoms, fruits 
and seeds, and enormous damage is caused to trees 
and plants by limiting their seed bearing powers. When 
these fruits are of commercial importance like the plum, 
the horticulturist classes the "plum curculio" as a 
first class pest and a subject for investigation by the 
economic entomologist. If I mention once again the 
cotton-boll weevil, and cite as a further example of seed 
destruction the strawberry weevil, the danger of this 
sort of insect to plant life may be appreciated. It is 
of course the larva that does the injury, and curculio 
larvae are all more or less grub-like in character; mostly 
white like the generality of internal feeders, and usually 
with a brown chitinous head furnished with well-de- 
veloped jaws or manidbles. 

Blossoms, fruits and seeds furnish only one article 
of diet for weevils and their larvae: many bore into 
the stems of herbaceous plants, as the rhubarb weevil; 
others bore into wood tissue like the w^hite pine weevil, 
and the latter, by killing off the leading shoots, fre- 
quently distorts a tree to such an extent as to make 
it commercially useless. A comparatively small number 
are external feeders on plant tissue like the clover- 
leaf beetle; a few make tubes or other cases out of the 
leaves on which they feed, and some cause galls or 



yo 



INSECTS 



other enlargements. There is, therefore, scarcely a 
method of attack that is not represented among the 
snout beetles. 



WW 





4 :>l^uu^iu and ili. lar\ . 



The Scolytids or bark beetles deserve separate 
mention, as they are among the most dangerous of all 
tree enemies and the greatest destroyers of wood tissue, 



THEIR RELATION TO PLANTS 71 

living or dead. The name bark beetle is a misnomer 
for many of the species, which never bore into or 
under bark at all; but it applies well to a very large 
number that make characteristic borings or galleries 
beneath the bark or in the sap-wood. In forms of 
which the common fruit bark beetle may be considered 
typical, the adult bores a longitudinal channel in the 
sap-wood and lays eggs on each side in little notches 
cut for that purpose. These beetles are all more or 
less cylindrical, slender and elongate, with a very short 
or scarcely perceptible snout and well-developed jaws 
or mandibles. The larvae that hatch from the large 
white eggs are of the usual grub-shape, white with 
brownish head, and each larva makes its burrow at 
right angles to the main gallery, diverging a little up- 
ward or downward as it increases in size so as to avoid 
its neighbors, and making a pattern so distinctive 
that the species may be recognized by its borings alone. 
Quite usually beetles of this character attack trees that 
are a little weakened or unhealthy, but some take to 
perfectly sound trees and cause serious trouble. Other 
species bore into the heart wood, their galleries being 
cylindrical, often blackened or discolored, and these 
are sometimes called shot-hole borers. 

No kind of tree is exempt from the attacks of 
such beetles, and thousands of acres of forest lands 
in all sections of the United States are annually de- 
stroyed by them. And much timber is rendered useless 
or lessened in value by the borings which disfigure or 
weaken it, where the life of the tree itself is not threat- 
ened. In trunk, in twig and even in the roots these 
Scolytid borers are found, and our knowledge of them 
still leaves much to be desired. Only a small propor- 
tion of our species are actually known, and their classi- 
fication at present is merely tentative. They are re- 



72 INSECTS 

ceiving more attention now than ever before, and they 
merit more attention than they are receiving. 

Altogether, the Coleoptera, among the dominant 
orders, furnish a very large number of destroyers of 
plant tissue living and dead, and many that may be 
ranked as destroyers of plant life. 

The order Lepidoptera includes the butterflies and 
moths and their larvae are known as caterpillars. Cater- 
pillars with few exceptions feed on plant tissue, hence, 
as a whole, the members of the order may be consid- 
ered as enemies of plant life. Mainly they are open 
and above-board enemies: direct feeders upon the leaf 
tissue, without modification or concealment. Such 
feeding in itself does not endanger plant life except in 
cases where there is an unusual number of caterpillars 
or the plant is one that will not survive defoliation; 
therefore the number of species dangerous to plant 
life in this way, is not really very great. There are 
such species, of course, for in the State of Massachu- 
setts there are hundreds of conifers dead as the result 
of defoliation from gypsy moth, and in general, any 
species that can completely strip a tree may cause its 
death. 

A comparatively small number of Lepidopterous 
larvae are borers in woody tissue, and these are mainly 
members of the families Sesiidce, CossidcB and Hepi- 
alidcc: all Tineites under the modem classification. 
The Sesiids are small clear-winged moths resembling 
wasps in appearance, and their larvae bore into trees 
and in the stems of herbaceous plants. The peach 
tree borers are types of the former, working under the 
bark at the surface of the ground and often causing 
the death of young trees; the squash borer is a type 
of the latter, boring into the stem of the plant at almost 
any point; but most often at the base. Both types 



THEIR RELATION TO PLANTS 



73 



frequently cause the death of the plants attacked; 
but there are others, like those attacking the trunks 
and branches of oak and maple, that may infest their 
host for years without causing obvious harm. Not 
only the tissue above ground is attacked, for one species 




Fig. 29. — The peach bor 



'sa; male above, female below. 



at least occurs on the roots of grape, and others are 
underground on oak. 

The Cossids are much larger forms and correspond- 
ingly more dangerous. The European Zeiizera pyrina 
or wood-leopard moth, which has been introduced 
into the eastern United States, frequently girdles 
young trees and often weakens the branches of older 
ones to such an extent as to make them easy victims 



74 



INSECTS 



to wind storms. Some of our own carpenter worms 
make simpler borings; but owing to their methods 
of work, leave sore spots that often form points of en- 
trance for germs of deca^^ Thousands of oak trees in 
the eastern United States are "doated" as the result 




Fig. 30. — Wood-leopard moth, Zeuzera pyrina: a, b, larva; c, male; d, female 
moth; e, larva burrow. 



of the work of these borers; stunted in growth and 
useless as timber. Fortunately the number of species 
is small and very few of them are at all numerous in 
specimens. 

The Hepialids are very ancient in type and they 
are few in number of species and specimens. The 
larvae are large and make large channels in roots and 



THEIR RELATION TO PLANTS 75 

trunks; but I have never known of any serious injury 
done by them. 

There are many others among the Tineid famiHes 
that are borers in herbaceous and shrubby plants and 
some cause gahs or other abnormal swellings in the 
infested stems; and there are many others that mine 
or bore in leaves, causing a great variety of disfiguring 
injury, but rarely anything that threatens the life of 
the plant itself. Many of these little caterpillars and 
a few larger species make cases or covers of the most 
diverse character, and others live in shelters spun by 
the members of one brood fi'om a single laying of eggs. 
Some live altogether in silken tubes spun by the cater- 
pillars, and of these some feed underground on the 
roots of com and other plants. Quite a number feed 
inside of fruits, like the Codling moth of the apple or 
the berry moth of the grape, and a few get into seeds 
like the Angoumois grain moth. 

We have, then, among the Lepidoptera, a very large 
number of feeders on vegetable tissue, that destroy 
portions of the plant without endangering its life, 
and a comparatively few that are really dangerous to 
the existence of the organism attacked, however much 
it may be injured from an economic standpoint. 

The order Hymenoptera contains a large number 
of species of very great interest: some of them vitally 
important to the continuation of plant life, and on the 
contrary a few that are destructive to it: but it is 
interesting to note that among the bees which have been 
shown in the preceding chapter to be among the great- 
est benefactors of plants, we should also find an element 
of danger. Plants suffer from "blights," "rusts," 
"scabs" and a variety of other diseases and, recently, 
plant pathologists have charged that bees in their 
visits to flowers engaged in the beneficial work of 



76 INSECTS 

pollination, at the same time carried also the germs 
of fire-blight and similar diseases, introducing them 
into the sensitive tissues of the blossom. It is an old 
story, of course, that disease organisms frequently find 
entrance through wounds made by insects; but that 
is merely putting the insects on a par with other causes 
that produce abrasions, cuts or bruises: this is a dif- 
ferent matter, the insect being charged as the active 
transmitter, much as a fly carries typhoid germs to the 
human organism. 

Direct plant feeders are found among the Hymen- 
optera in the Sessiliventres, — "saw-flies" and "horn- 
tails," — which derive their technical name from the 
fact that the abdomen is joined to the thorax for its 
full width and is thus sessile, while in the majority of 
the species in this order it is stalked or pedunculate, 
attached at a narrow point only. The saw-flies are 
somewhat clumsy in appearance and more sluggish 
than the other Hymenoptera, the body rather uniform 
in size from end to end, the wings large, with many 
complete cells, and folded over the back when at rest. 
They derive their common name from the fact that the 
ovipositor is made up of parallel blades variously 
toothed at the edge, by means of which the female 
cuts a slit or pocket into a leaf, stem or twig, for the 
reception of an egg. The larvae that hatch from these 
eggs are caterpillar-like in appearance but have five 
pairs of abdominal prolegs instead of four or less, as 
is the case in the true caterpillars. They are mostly 
feeders on foliage, like the currant worm, and they 
sometimes appear in enormous numbers ; but they do not 
often threaten the life of the plant. Some of them only 
scrape the surface of the leaves like the pear slug, 
while others eat characteristic holes in them like the 
blackberry saw-fly. A considerable number are gall- 



THEIR RELATION TO PLANTS 

willow, the excrescences 



77 
beincr 



makers, largely on 
quite characteristic. 

The "horn-tails" have the ovipositor modified into 
an augur-like process for making holes in plant tissue, 
and the larvae are mostly borers: some in wood, most 







Fig. 31. — The currant worm: a. adults; b. larvs in various stages of devel- 
opment; c, pupa; e, eggs along veins on leaf. 



of them in shrubs or grasses. These very often threaten 
the life of the plant attacked, especially when wheat or 
other grasses are infested. But on the whole the number 
of these boring species is small, nor are they often 
numerous in examples. 

A very characteristic set of species is found in the 
"gall-wasps" or Cynipids now ranked as a superfamily 



78 INSECTS 

under the term Cynipoidca. These gall- wasps produce 
in the plants attacked abnormal swellmgs or growths 
known as galls, which are constant for every species 
and differ as the species differ. Thus for those forms 
whose life history is known, the gall is as good an index 
to its kind as a specimen of the wasp. And the re- 
markable point is, that the gall is purely a production 
of the plant and the insect has, apparently, nothing 
at all to do with it. The female lays the egg and in 
due time a minute larva hatches. Immediately there 
begins to develop around this larva an abnormal growth 
centered by a smooth cell in which the larva lies, a 
white helpless grub, feeding upon the exudations that 
come from the inner side of the cell. The relation be- 
tween the irritation set up by the minute larva just 
out of the egg and the remarkably complicated struct- 
ure of plant cells built up around it has never been 
clearly elucidated and offers an excellent opportunity 
for research. Some galls are spongy in texture, some 
are solid; some are filled with radiating fibres extend- 
ing from the central cell to the covering sphere; some 
are no larger than necessary to accommodate the insect 
and yet others are huge bladder-like affairs, out of all 
proportion to the size of the larva. Some galls are on 
leaves, some on twigs and branches and a few are on 
roots. On the roots and stems the growths are often 
corky or woody, and sometimes mere enlargements 
of the normal growth. More generally the galls are 
unicellular, i.e., they have only a single central cell 
containing one larva; but very often also they are 
multicellular, a large growth containing many larval 
cells which, in turn, may be very regularly or very 
irregularly disposed in the larger mass. 

These gall-wasps have a number of very interesting 
features. Some of them appear, year after year, males 



THEIR RELATION TO PLANTS 



79 



and females, without variation ; always making the 
same kind of gall. Others appear in spring from over- 
wintered galls, normal males and females: the latter 
lay eggs, galls appear, but from them only females 
make their appearance; these in turn lay eggs and from 
their galls males and females appear again the year 
following. This is termed an "alternation of genera- 
tions" and so long as the galls are similar and the fe- 




FlG. 32. — .'Vn oak Rail, made by Cynips q-spongifica: a, showing the 
larva in its cell; b. exit hole of adult. 



males are similar, no confusion is caused. But it some- 
times happens that the summer generation is very 
different in appearance from the hibernating form, 
while the gall itself is different and on a different kind 
of tree, so that there appears to be no sort of connec- 
tion between them until the life history has been com- 
pletely followed out — -no light task in species of this 
character. For some species no males have ever been 
found and, so far as we know, these are maintained 
by parthenogenetic females alone. 



8o INSECTS 

It also happens sometimes that a normal constituent 
of plant tissue, like tannin, is greatly intensified in the 
gall structure which may contain many times more 
tannic acid than any other part of the tree. The galls, 
therefore, become of commercial value and in some 
localities the oak forests yield a considerable revenue 
from this source. 

Few Cynipid galls are really injurious to the plants 
on which they appear. Those on the leaves are never 
so; those on twigs are rarely so; those on the larger 
branches sometimes cause a choking and sometimes 
a weakening that results in a fracture under strain; 
but frequently a badly galled branch will in its de- 
velopment split ofif and shed the old galls. Root galls 
sometimes threaten the life of a plant; but most of 
the fatal galls found on trees, shrubs, and vines are due 
to other causes. 

In the Diptera we have plant feeders in great variety, 
and many of them endanger the life of the plants at- 
tacked; but they have a decided preference for soft 
tissues and there are no borers in solid, living wood. 

Among the long-legged, mosquito-like species with 
long antennae, the crane-flies have larvae that live 
underground and feed on the plant roots. They are 
sometimes called "wire-worms" because of their long 
slender form, and "leather-jackets" because of their 
texture. They differ from the beetle larvae that are 
also called wire-worms, by the more cylindric shape, 
the more pointed head, and absence of legs. Their 
feeding on roots is sometimes extensive enough to 
cause the death of the plant attacked. The crane- 
flies are the largest of the long-legged forms, some of 
them measuring with legs extended nearly three inches. 

The gall-midges are at the other extreme and in- 
clude very small species with very long, often prettily 



THEIR RELATION TO PLANTS 



8i 



Ijeaded antennae. Their larvae are little footless grubs, 
peculiar by having a single chitinous rod or anchor- 
like structure known as a breast-bone, which serves 
to scrape the plant tissue on which the creature feeds. 
These gall-midges or Cecidomyiids attack a great va- 
riety of plants at all sorts of points, and cause a great 




Fig 



33. — The pear midge. Diplosis pyrivora: a, female adult; c, pupa; other 
references to structural details. 



variety of deformations that are commonly known 
as galls, although they differ totally in character from 
the galls caused by the Cynipids. For instance, the 
pear midge lays its eggs in the pear blossom; the 
larvae enter the seed capsule of the fruit and the latter 
becomes somewhat abnormal in shape so that to the 
practised eye the galling is perceptible. The Hessian 
fly lays its egg in the sheath of the wheat leaf near 
6 



82 INSECTS 

the ground; the larva starts its feeding there and 
causes an injury which the plant, in its efforts to repair, 
marks by an enlargement. A midge lays its eggs in 
the tip of a willow shoot, the larvae feed at the base 
of the forming leaves and the plant becomes crippled, 
producing a cabbage-like head instead of a shoot with 
developed foliage. And so we have every gradation 
from a feeding without any perceptible enlargement 
or swelling at all, to a well-formed abnormity formed 
by a crippling of the natural growth, and not a distinct- 
ly separate structure, unrelated to normal growth. 
There are other types of midge-galls, like those on the 
grape, which are mere fleshy swellings of the normal 
tissue, and sometimes more characteristic enlargements 
of infested twigs; but generally no separable galls. 

As to the actual injury caused, that varies enor- 
mously. Many of the midge-galls cause no real or per- 
manent injury whatever to the plant attacked. Others 
destroy either the plant or the seed beyond all chance 
of recovery. These midges are to be accounted among 
the most serious plant enemies, although soft her- 
baceous plants and grasses are more apt to suffer; 
very few of them occurring in genuinely woody tissue. 

Among the Muscid flies resembling in general type 
and appearance the house-flies, the Anthomyiids are 
the most troublesome and dangerous. They attack 
a very great variety of plants and may be miners in 
the thick leafed forms like beets, or feeders in roots 
like those of the radish, cabbage or onion. And these 
root maggots are very generally fatal to the plant 
attacked, so that their rank as destroyers is high. 
The maggots themselves differ very little from the 
other Muscid larvs; in fact not at all to ordinary view, 
and they gain their food in the same way by scraping 
and disintegrating the tissue and then absorbing the 



THEIR RELATION TO PLANTS 83 

liquid mess. There is, in consequence, nearly always 
an appearance of decay associated with the work of 
such maggots, and that appearance is very real in 
cases where the wounded surface gives entrance to 
soft rots of various sorts. As for the leaf miners, their 
work is not so destructive in character, although natur- 
ally every injury that impairs the usefulness of the foli- 
age to the plant, reacts upon the entire organism to 
some extent. 

There are other maggot-like larvse that work in 
plant or fruit tissue such as the apple maggot, the 
orange fruit fly and a considerable number of other 
fruit flies which, while they seriously affect the com- 
mercial value of the product, do absolutely no injury 
to the plant, since neither the seed nor the tree itself 
is affected. Only the pulpy covering to the seed is 
harmed and that is of no importance at all to the plant 
however much it may be to man. 

We have thus reviewed very briefly the various 
orders of insects, and have called attention very cur- 
sorily to the kind of injury which is caused by them. 
From the time it appears above ground to the period 
of maturity, almost every species of plant serves as 
food for insects; and if it survives their various as- 
saults and reproduces its kind, its decay and return 
to the inorganic constituents from which it made its 
growth is hastened by yet other species. And that 
applies as much to the forest giant, aged hundreds of 
years, as to the humble cabbage plant that runs its 
course in a single season. 



CHAPTER IV 

THEIR RELATION TO EACH OTHER 

It has been brought out, directly and incidentahy, 
that insects are among the most proHfic animals. If all 
the feeders on vegetable life were allowed to develop 
absolutely without check during two successive years, 
the first of them would see every green thing swept 
from the face of the earth, and the second would destroy 
all possibility of the future recurrence of fully go per 
cent, of all the existing plants. And if during the same 
period all forms feeding upon vertebrate life were 
allowed to develop in the same way, our globe would 
be a practically uninhabited and uninhabitable desert. 

But the very fact that they are so remarkably 
fecund is an indication that they have many dangers 
to contend with and many difficulties to surmount 
before reaching the adult or reproductive stage. Under 
normal conditions and in the long run, one pair of 
moths, producing say 500 eggs, are represented next 
year by another pair of the same species, and no more: 
that is, out of 500 eggs, producing 500 caterpillars, 
498 are destroyed in some way. Naturally this varies 
from year to year to some extent, favorable conditions 
permitting an increase one year and causing a decrease 
at some other period. And, equally of course, while 
some broods may be completely destroyed, others 
may all come to maturity. 

Now the very fact that an insect exists at all, is 

proof that it is adjusted to its surroundings, including 

its parasitic and predatory enemies and all the other 

natural checks. And when it occurs as an abundant 

84 



THEIR RELATION TO EACH OTHER 



8S 



species it means that this abundance is normal, and 
that the natural adjustments are such as to maintain 
that abundance in relation to its food unless man in- 
terferes, and the results of such interference will be the 
subject of further discussion, later. The important 
point is that a species abundant in number of specimens 
has become so in spite of the combination of all its 
natural checks and, condi- 
tions remaining equal, will 
maintain itself in the same 
ratio, just as a rare species 
barely maintains itself 
against the combination op- 
posing it. It happens again 
and again that a common 
species becomes more than 
usually abundant, and it oc- 
curs occasionally that a 
species normally rare escapes 
from its control and makes 
its mark as an injurious 
form. But even without 
human interference this 
rights itself in a season or 
two: the common species 

may even be reduced for a time to less than its usual 
numbers, while the rare species drops back out of sight 
of all but the collector. The checks or natural enemies 
of neither form ever increase sufficiently under normal 
conditions to do more than restore the original ratio. 
What then are these checks that prevent with such 
absolute effect any undue increase of a species despite 
enormous reproductive powers? They are really very 
numerous and of decidedly unequal effect on the dif- 
ferent forms. We have weather, disease, insectivorous 




dyiduct 

Vegine 
Oyipositor 

34. — Ovaries of a bee show- 
ing the different parts. 



86 INSECTS 

animals of many species, birds and, last but by no means 
least, in the war of insect upon insecc, the predatory 
and parasitic forms. It was almost inevitable that 
in the course of development some originally plant- 
feeding insect would find itself in position to get its 
plant juices at second hand, so that, instead of feeding 
upon plant tissue directly, it fed upon its next neighbor 
and got the same material indirectly. We have, even 
now, examples in Hemiptera and Coleoptera of species 
that feed upon vegetable tissue and also upon other 
insects when they get in the way; or of species which, 
while normally predatory, occasionally feed upon 
vegetation. In the Hemiptera I know of examples of 
this kind in the Pentatomidce and in Coleoptera they 
occur in the Carabidce and CoccinellidcB. And the 
step from predatory to parasitic habits is an easy one, 
albeit a much greater specialization. Insect feeders 
upon vegetable life were first developed; predatory 
forms came very soon afterward and occur in almost 
if not quite all orders; parasitism on other insects 
came much later, and is best developed in the highest 
and most specialized orders, being practically non- 
existent in the lower or primitive types. Parasites 
on higher animals, such as the biting and sucking lice 
which occur in the Neuroptera and Hemiptera, are not 
in any way comparable with the insect parasites that 
occur in the Hymenoptera and Diptera, to which highly 
specialized and most recently developed orders the 
great majority of all the parasites on insect life belong. 
There are few true parasites in any other of the orders. 
Among the Thysanura we have no parasites and no 
predatory forms. In the Neuroptera we have many 
decidedly predatory forms and the beginnings of par- 
asitism. The Neuroptera as limited in Chapter I, con- 
sists of a number of remnants of earlier types, agreeing 



THEIR RELATION TO EACH OTHER 87 

only in the fact that the wings have numerous longi- 
tudinal and transverse veins, breaking them up into 
many small areas so as to appear more or less netted. 
But in the detailing of habits and suggesting lines of 
descent, further subdivision is convenient. 

Thus the Ephemerida or May-flies contain neither 
parasitic nor predatory forms. In the larval or early 
stages they live in the muddy bottom of streams, feed 
on the organic hfe contained in this material and, in 
the adult stage, do not feed at all. Yet it is here that 
the highest orders get their start and in them predatory 
and parasitic types are numerous. 

In the Plecoptera or stone-flies we have a similar 
record except that the mouth structures in all stages 
are much better developed. Here the larval stages 
are passed under submerged stones, usually in running 
streams, and the food consists of such floating organic 
material as is carried in. The adults in spite of their 
rather well-developed mouth organs have not been 
observed feeding. 

The Mallophaga or biting lice are animal parasites 
and are dealt with in Chapter VII, and the Corrodeniia 
or book- and bark-lice are feeders on dry or dead or- 
ganic matter; not really scavengers, but nevertheless 
removers of dead material. 

The order Isoptera, containing the Termites or 
white ants, is interesting from its communal life and 
will be referred to again; but it depends entirely upon 
vegetable matter for its subsistence and mainly upon 
dead tissue. 

The order Platyptera is the first of the Neuropterous 
types to contain predatory forms and, while it is aquatic 
like the Plecoptera, has the metamorphosis complete and 
is altogether much better developed, albeit the adults 
are loose-jointed and flabby enough, when handled. 



88 



INSECTS 



The larvae have the jaws and other mouth parts well 
developed and feed upon other soft-bodied aquatic 
forms. They assist in checking the increase of the 
May-flies and stone-flies, and are themselves hunted 
by fish, which keep them down to normal numbers. 




Fig 35. — The "hellgrammite" or "Dobson": a. larva; 6, pupa; c, male adult; 
d, head of female. 



The order Neuroptera, strictly speaking, contains 
only predatory forms and the beginning of parasitic 
habits. With few exceptions the species are terrestrial. 
The families Coniopterygidcs, ChrysopidcB, HemerohiidcB 
and Myrmeleonidcs, are rather similar in the larval 



THEIR RELATION TO EACH OTHER 89 

stage; the body being more or less ovate, set with 
lateral tubercles giving rise to groups of bristles, while 
the mandibles are long, slender and pointed, peculiar 
in being grooved on the inner side so that the body 
juices of the prey may run down through them into the 
mouth cavity. The Chrysopidce are known as Aphis- 
lions, and when they capture a plant louse it is held 
up, impaled on the mandibles, until the juices are all 




Fig. 36. — A lace-wing fly, Chrysopa oculata- a, eRgs on stalks; b, larva; d. same 
feeding on pear psylla; e. the cocoon from which /. the adult, has escaped. 

absorbed; then the dry carcass is thrown away. The 
Myrmeleonidce or ant-lions build a pit in the sand to 
entrap any unwary insect that may come along, and 
anything that does come is seized in the same way and 
exhausted, the empty shell being thrown out later. 
Not all ant-lions build pits and not all the members of 
the families named agree in all respects with the general 
statements as to larval form and characters; but for 
the majority of the species that come under observa- 
tion they are correct. 



go 



INSECTS 



The Raphidiidcc are very curious creatures peculiar 
to the Pacific Coast, in which the head and prothorax 
of the adult are greatly elongated and it, as well as 
the slender elongated larva, is predatory. In the pre- 
ceding families, while the larvae are voracious feeders, 
the adults feed little or not at all. 

The MantispidcB are similar to the Raphidiidce in 
the elongation of the prothorax; but the head is much 
shorter and the fore legs are enormously developed 
for grasping, this series being also predatory in the 
adult stage. But the interest- 
ing feature is that we find in 
the larva the first tendency 
toward parasitism and the 
specializations accompanying 
it. The eggs are laid on stalks 
like those of the Aphis-lions, 
but the resulting young live 
for months without food, until 
the egg sacs of certain Lycosid 
spiders have been formed. 
The lucky larva that finds 
such a sac bites its way through the covering and feeds 
upon the contents. As it feeds and grows it loses its 
large head and long legs, and becomes helpless except 
to feed upon the surrounding material which serves 
to bring it to maturity. While in a general way these 
insects are said to be parasitic in the egg sacs of spiders 
yet this is not really a true parasitism at all; it is 
simply a feeding upon the eggs and young spiders as 
any predatory species might feed upon them, the only 
difference being that here the larva makes itself at 
home and does its feeding gradually, so as to secure 
enough to reach maturity. 

The order Mecoptera is a curious one, only a few 




Fig. 37. — Mantispa species 
from above and in outline from 
side. 



THEIR RELATION TO EACH OTHER 91 

genera and species remaining as representatives in 
our fauna. All of them are feeders on animal matter 
and most of them are predatory in all stages. The 
best known forms are the scorpion flies, so called from 
the curious anal appendages of the male, which bear a 
remote resemblance to a scorpion tail without its ter- 
minal sting. The larvae, which are somewhat caterpillar- 
like, live under ground and prefer rather damp places. 
There are not enough of the insects to make them of 
any importance as checks to anything in particular, 




Fig. 38. — A Panorpa or scorpion fly and its larva. 

and as they feed rather indiscriminately on soft-bodied 
insects, chiefly flies, they are of no economic value. 
It is probable that this order represents the type from 
which the Diptera and Hymenoptera were derived. 

The caddice flies or Trichoptera are aquatic in the 
larval stages and as aerial adults do not feed at all. 
As larvffi they derive their name from their habit of 
making cases or "caddices" of various shapes from 
little sticks or stones closely fitted and held together 
with silk. Some of the species are feeders upon vege- 
table matter, others appear to be predatory, or feeders 
upon animal matter at least. They are very numerous 
in specimens and species, but naturally do not influence 



92 



INSECTS 



any terrestrial forms. The adults have the wings 
covered with fine hair and some of the small forms 
resemble Tineid moths so closely that they are con- 
fused with them. It is believed, indeed, that this is 
the direct ancestral form of the Lepidoptera. 

And now comes the order Odonata, containing the 
dragon flies, large and small and all of them predatory 
in habit in all stages. As larvae they are aquatic, living 
in ponds, streams or even the more permanent pools 



Jfek 





Fk;. 3g. — IJration Hy ainl its development; larva and pupa feeding at i and 
3; 2, nymph ready to change; 4, pupa skin from which s, the adult, has emerged. 



and puddles; some of them active, inoving about 
freely among the vegetation, others sluggish, lying in 
the soft bottom mud or under stones or other shelter, 
waiting for things to come their way. They are pecu- 
liarly adapted by their elongated hinged under lip, 
or labium, to reach such small creatures as fate may 
send within half an inch of them and, with a little for- 
ward jerk of the body and a rapid extension of the 
armed labium, the prey is seized. This prey varies in 
character according to the habits of the larvae. Some 
of the more active forms destroy a large number of 



THEIR RELATION TO EACH OTHER 93 

mosquito wrigglers and display surprising skill in cap- 
turing them. Others take in anything that comes along, 
be it insect, crustacean, or even small pollywog or fish. 
They have no aversion to their own kind and will eat 
each other if food is scarce or not easily obtainable. 
As for the adults, anything that comes within their 
range will answer as prey ; but in general small flies are 
the most abundant victims. The common name "mos- 
quito hawk" indicates one common article of food, 
and there is no doubt that a very large number of 
specimens is eaten. In some cases the mosquito pest 
may even be materially lessened by them during the 
period of adult flight; but they scarcely rank among 
the really controlling checks because they are active 
only during the day while the mosquitoes prefer the 
night for their flight; and the dragons prefer the open 
sunlit area around ponds or along streams, while those 
mosquitoes that fly at all during the day prefer shel- 
tered, shaded and darkened places. Most of the dragon 
flies are simply general predatory feeders on any soft- 
bodied insects which they can overtake, rather than 
specific enemies of any one form. 

In the order Hemiptera there are no parasites on 
insect life. The lice, parasitic on vertebrate animals, 
are elsewdiere considered, and nowhere else do we find, 
in this order, any approach to true parasitism. Of 
predatory forms there are a large number; indeed 
among the aquatic species the majority are predatory, 
feeding on other water insects and even fish. Among 
these the little Corisidcc and Notonectidcc, water-boatmen 
and back-swimmers, are especially vicious and active, 
easily forming a very notable factor in the control of 
aquatic insect life. 

Among the terrestrial forms the entire series Hom- 
optera lacks predatory types; in the Heteroptera we 



94 



INSECTS 



find that modification of habit which is elsewhere re- 
ferred to — a tendency to get plant juices at second 
hand, by sucking the juices of such soft-bodied larvae 
as have just fed upon plant tissue. This is found in 
quite a large number of the families, making a con- 




Fir,. 40. — The wheel-bug, Prionidus cristatus, in all its stages. 



siderable series of species that feed indifferently on 
plant or soft insect tissue. But there is also a large 
number of species with short stiff beaks and small 
narrow heads that are distinctly and exclusively pred- 
atory. These are the ReduviidcB commonly known as 
" pirate " or " assassin bugs " from their habit of stabbing 
or piercing the specimens upon which they feed. 



THEIR RELATION TO EACH OTHER 95 

These bugs are of considerable importance as checks 
to certain plant feeders and as they feed in the same 
way throughout their life, each individual accounts 
for a notable number of victims. Their weak point 
is the limited power of reproduction. Most of them 
lay only a small number of eggs and have only a single 
or at most two broods during the season. As a control 
factor, therefore, they lack flexibility and do not rise 
to any sudden increase in the plant feeders. There is 
a common species that in New Jersey feeds on the 
larvae of the elm-leaf beetle, and each season is busily 
engaged on the infested trees in fair numbers. In 
years when the beetle is not abundant the marks of 
its feeding are quite conspicuous; but in a season when 
the beetle is unusually plentiful and destructive, the 
bugs are present in almost exactly the same numbers 
and their work is absolutely unnoticeable when effec- 
tiveness is most urgently needed, nor does there seem 
to be any considerable increase during the season fol- 
lowing such an abundance. This same feature exists 
with most of the species known to me and limits their 
usefulness to very narrow bounds; they constitute 
one check which is almost a fixed quantity and to which 
the host insects are adapted. 

The order Orthoptera, including roaches, grass- 
hoppers, locusts, crickets and the like, contains no true 
parasites and but few predatory forms. Some of the 
roaches are omnivorous and pick up occasional speci- 
mens of insects and animal matter; but they can 
scarcely be ranked as important checks to any other 
species. And so the Mantids or soothsayers are vora- 
cious feeders, preying upon almost any sort of insects 
which they can secure; but they are few in number 
both as to species and specimens, while their food is 
so various that they are not of importance in the life 



96 



INSECTS 



cycle of any one kind. Crickets there are of many 
sorts, and some of these are general feeders, eating 
each other as freely as they do vegetation and other 
things. The tree-crickets are more definitely predatory 
in habits and feed largely upon plant lice; but they 
also are too few and too slow in reproducing to be able 
to exert a very important influence on the increase of 
their prey. Furthermore, they are limited as to the 
places which they inhabit, and no field crops of any 
sort harbor them. 




Fig. 41. — Stylops and its development: a. female in body of bee; b. same in 
outline; c, d. male from above and side. 



In the order Coleoptera or beetles we have few 
truly parasitic forms. We may for the present consider 
the family Stylopidcc as true Coleoptera and these are 
found in the abdomen of various insects, chiefly bees 
and wasps although some Hemiptera and perhaps 
other orders are also infested. But they are so very 
rare that they exert little influence on the numbers 
of the species which they infest. Their life history 
and complicated metamorphoses are extremely inter- 
esting, the female being wingless and living in the 
abdominal cavity of its host, with the head projecting 



THEIR RELATION TO EACH OTHER 97 

between the segments. The young are minute, active 
creatures Hke those of the bHster beetles, and run 
about freely until they find some suitable host in which 
their future development may be continued. Then 
they lose their feet and prominent jaws, becoming 
grub-like and inactive as the necessity for seeking 
food is removed. 

The blister beetles or Meloidcv are semiparasitic 
in habit and are quite numerous in specimens and 
species. Some of them live in the egg-pods of grass- 
hoppers and others in the nests of digger bees, chiefly 
Andrenidce, feeding on the food stored by their hosts 
and, incidentally, devouring the egg or young larva 
of the bee. These blister beetles will be referred to 
again in their relation to man, but in their relation to 
the insects upon which the larvae feed they rank as most 
effective checks. The female beetle lays her eggs on 
flowers or on the ground as the case may be, and the 
resulting larvae are active creatures with long legs 
and large jaws known as " triungulins. " These are 
able to go for long periods without food and they seek 
either a grasshopper egg-pod or some plant or flower 
frequented by bees, as the need may be. The forms 
that hunt egg-pods, when they succeed in finding one, 
immediately begin to feed. The forms that wait for 
bees attach themselves to almost any hairy insect 
that comes along and the lucky specimen that gets 
upon a bee of the right kind is carried by it into its 
burrow. When the bee with its burden of pollen plus 
the parasite gets into the cell which it is filling with 
food for its larva, the triungulin slips off, devours the 
egg of its host as soon as laid, and that suffices to 
bring it to the end of the first stage. From this point 
the changes in both kinds of larvas are similar. They 
are in direct contact with abundant food, the legs 
7 



98 



INSECTS 



and large jaws are useless and they enter what is known 
as the "Carabidoid" stage in which they resemble the 
larvae of ground beetles. Continued good feeding re- 
sults in a further reduction of parts and the third instar 
is even more grub-like and therefore termed the "Scar- 
abidoid" stage, during which it exhausts its food sup- 
ply, — either the egg-pod or the stored material in the 




Fig. 42. — Development of a blister beetle: a, grasshopper egg pod with tri- 
ungulin at // b, a few grasshopper eggs; c, triungulin; d, carabidoid larva; e, 
scarabidoid larva. 



bee cell. Then the outer skin hardens, the larva loses 
shape and enters the coarctate stage in which it lies 
dormant until the period when the adult is due to 
appear. When this comes, the hardened larval skin 
is shed and the true pupa, of the ordinary beetle type, 
appears. When the proper hour arrives, as if at the 
striking of a clock, the transformation to the adult 
is completed and the blister beetles emerge, ready to 
feed and propagate. And now the story changes, for 
while we can have only words of praise for those larvae 



THEIR RELATION TO EACH OTHER 



99 



that feed on grasshopper eggs, the adult beetles almost 
without exception are devourers of plant tissue. Their 
habit of coming to maturity at about the same time 
brings clouds of them upon their food plants at once, 
and gardens and certain truck crops suffer. It becomes 
a question then, whether the insects are economically 
more useful as destroyers of grasshoppers or more 
destructive as feeders on crops. As to the species 
feeding in the nests of bees, they are without question 
economically injurious in all stages. 




Fig. 43. — Two common blister beetles: a. Macrobasis unicolor; b, Epicauta 
pennsylvanica. 



But there can be no doubt either that in regions 
where grasshoppers are very abundant, as they are 
in the Rocky Mountain and some of the southwestern 
areas of the United States, these blister beetles are a 
most important check and one that has a large amount 
of flexibility in effectiveness despite the fact that there 
is only one annual brood. This is obtained by the 
large number of eggs laid by the female, which in some 
species runs into the thousands. The adults make no 
attempt to place these near egg-pods, but only on 
ground where such pods are likely to occur. It is up 
to the young larva to find its own hotel accommoda- 
tions or starve to death. When grasslioppers have been 
scarce and pods are widely scattered, a very large per- 



TOO INSECTS 

centage of the triungulins never get beyond that stage; 
but when there has been an abundance of hoppers and 
egg-pods are numerous, matters are easier for the 
enemy and a larger percentage secures food. In this 
way it happens that after a season of grasshopper 
abundance a season of bhster beetle abundance is al- 
most certain to follow, and any abnormal increase of 
the former is almost sure to be checked by the cor- 
responding increase of the latter. 

A very material change is introduced by the migrat- 
ing habit of some of the host species. Blister beetles 
are not great travellers, while a grasshopper swarm 
may fly for hundreds of miles, clear out of the faunal 
range of their check. But in such instances, while 
they may have a year or two of unusual freedom for 
development, they become in time victims of the un- 
favorable climatic conditions in their new surroundings 
and are crowded back into their natural domains, under 
the control of their normal enemies. 

While, in a way, it is correct to refer to these beetles 
as parasitic, they are not really more so than the Man- 
tispids that feed in spider egg-sacs, and in the case of 
those feeding in the cells of bees they are even less so. 
For here the egg or young larva of the bee is only eaten 
to remove the owner of the stored food and the real 
object of the "parasite" is the stored provender. It 
is therefore a robber rather than a parasite, unless we 
use the latter term in a very broad sense. 

As to predatory forms, the order Coleoptera con- 
tains a great number. All those species that have 
filiform or thread-like antennae, comprising the fami- 
lies Cicindelida: (tiger-beetles), and CarabidoB (ground 
beetles), HaliplidcB (diving beetles), and Dyiiscidcu 
(water tigers), are predominatingly feeders upon other 
insects. A few feed on vegetable tissues as well or as 



THEIR RELATION TO EACH OTHER loi 

an alternate, and a very few seem confined to a plant 
diet; but, as a whole, this immense series of species 
feeds on other insects in both larval and adult stage. 
Most of them are rather general feeders, taking all 
things that come in their way, and they are not at all 
particular whether this prey is another predatory form 
or a plant feeder. And we have species that frequent 
trees, shrubs and flowers as well as those confined to 
the ground: the smaller forms capable of feeding only 
upon eggs, the larger climbing trees for the caterpillars 





Fig. 44. — A caterpillar-hunting ground 
beetle and its larva. 



Fig. 45- — A common type 
of ground beetle. 



to be found on them. Some of the species have the 
advantage of being able to adapt themselves to the 
conditions found in cultivated fields and orchards and 
the number of larvse and pupae of plant-feeding forms 
that go under ground for pupation or hibernation that 
are destroyed by them is beyond all computation. 
While I do not recollect at this time any species that 
devotes itself to any one particular kind of prey, there 
is no sort of doubt of the reality of the check which the 
ground beetles exercise over the increase of plant- 
feeding forms — especially those which pupate on or 
under the surface. But we must limit this praise just 



INSECTS 



a little: none of them bother with such small fry as 
plant lice and scale insects and their cannibalistic 
habits do much to limit their usefulness. 

In the series of rove-beetles or Staphylinidao , which 
are scavengers as a rule, there are many small species 
that are predaceous, and what a battle goes on between 
these and other breeders in or among damp, decaying 
vegetation we can only guess when, with a sieve, we 
collect out of a handful of forest leaves sometimes a 
dozen species of adult beetles and hundreds of minute 
larvae and wriggling creatures of 
all sorts. The collector who cov- 
ers a dozen miles in a day and at 
night has a box of butterflies, 
beetles and other insects to show 
for it, has seen much; but he has 
seen nothing of the intimate life 
of insects as compared with the 
man who has spent the same 
period in an open glade in a 
deciduous wood. It is not in the 
open air and on the surface that 
the most interesting matters are to be observed; it is 
under the shelter of fallen leaves, in the very centre 
of a decaying stump or log, or beneath a stone and 
sometimes deep in the very soil that insect life man- 
ifests itself in its most wonderful ways. It means 
patient watching and persistent study to unravel all 
these mysterious happenings that come to our atten- 
tion, and it is because we have not yet done enough 
of this, that we know so very little about these rove- 
beetles and their minute allies; but we do know that 
they are not all scavengers at any rate. 

Among the Coccinellidce popularly known as "lady- 
birds," "ladybird beetles" or simply "ladybugs," 




Fig. 46. — A rove-beetle 
and its larva. 



THEIR RELATION TO EACH OTHER 103 

we find a very decided specialization as to the char- 
acter of the prey. Almost all the members of the family 
are predatory during the larval stage, but they are not 
general feeders; some of them are even very closely 
limited as to food, and form specific checks of the very 
highest importance. Remove one of these checks and 
the host may become immeasurably destructive: re- 
store it and, no matter how much the host has gained, 
the check will regain control. Plant lice and scale 
insects are the especial prey of these beetles and the 
facts just recited are within the observation of almost 
every student of entomology. We are in the habit of 
thinking of "ladybird beetles" as being red or yellow 
in color with black spots, and as nearly hemispherical 
or at least convexly oval in form. The form is quite 
constant indeed, but the colors are by no means all 
gay. Besides the red, yellow and black species there 
are those that reach to metallic blue and yet others 
that are dull or shining black with very little if any 
maculation. The variation in size is also considerable, 
for while we have giants half an inch in length, we 
have pIso midgets not much more than one one-hun- 
dredth of an inch over all. 

Is there any unusual increase of a plant louse or 
scale species: in a few weeks their ladybird enemies 
will be found to be on the increase as well, and very 
often, even before the end of the season, the control 
will be re-established; for many of these species have 
several broods during the year and plenty of food is 
conducive to quick development. Even a normally 
rare species may under such a spur become abundant. 
An example of such control I have seen on several 
occasions in the case of a plant louse that infests Nor- 
way maples, by the 15-spotted ladybird, which is not 
usually common. When weather conditions during 



I04 



INSECTS 



early spring favor the plant lice they increase until 
June, when the first hot, dry spell puts a period to their 
work. An unusually cold, wet spring will be accom- 
panied by an unusual abundance of lice, and on three 
occasions within twenty years when the cold, wet 
weather extended into late Jvme, infestation became 
so serious that the leaves were covered with honey- 
dew and soot-fungus, so that they choked and began 
to drop. But about this 
time the ladybirds were 
also in the running and 
had become so numerous 
that they were fast reduc- 
ing the plant lice and put- 
ting a period to the infes- 
tation. And then came the 
long deferred hot spell in 
early July, wiping out the 
plant lice as with a sponge 
and leaving thousands of 
beetle larvae without food. 
What did they do? First 
the larvae ate all the eggs 
of their own kind yet on the leaves; then they ate the 
helpless pupae getting ready to change to the adult stage ; 
then the large larvae ate the smaller ones and as they 
became full fed and pupated, they in turn became vic- 
tims to those that had escaped the slaughter. And before 
the end of July the 15 -spotted ladybird beetle was again 
a rare insect and no outward sign remained to tell what 
crowds of them had been on the scene a month before. 
But not all Coccinellids are able to increase so 
rapidly ; some species being strictly limited to one 
brood. The cottony maple scale in the east is con- 
trolled by the signate ladybird. Hyper as pis signata, 




^IG. 47. — 15-spotted lady-beetle: ( 
larva; b, pupa; d-g, adult varieties. 



THEIR RELATION TO EACH OTHER 105 

a little black species with one red spot on each wing- 
cover. About once every decade the scale escapes con- 
trol, and for a series of three or four years becomes in- 
creasingly abundant so that tree ow^ners are thoroughly 
scared and demand remedial measures. Experience 
has enabled me to assure these owners that when mat- 
ters arc apparently getting serious, the worst is over; 
because by the end of the third year the Hyperaspis 
has caught up with its host and almost every scale 




Fic. 48.— The signate lady-beetle. 

egg mass contains one or more beetle larvse feeding in 
and upon it. The year following, scales mav be difficult 
to find and the Hyperaspids are forced to other species 
upon which they fail to maintain themselves and 
perish — all save a few that find enough congenial food 
to maintain the species. 

What happens w^hen an insect of this character is 
entirely freed from its normal check, was demonstrated 
in California when the cottony cushion scale, I eery a 
purchasi, was introduced from Australia without the 
Vedalia cardinalis. In a few years the leerya had as- 



io6 INSECTS 

sumed the dimensions of a calamity and, as one excited 
grower informed me, even the hitching posts became 
infested. The introduction of the ladybird enemy 
which had been discovered in the native home of the 
scale turned the tables at once. In less time than it 
had taken the scale to overrun the country, the Vedalia 
aided by artificial breedings and distribution, cleaned 
it out, until now both scale and beetle barely maintain 
themselves. There are undoubtedly many other similar 
relations, but on this point we have yet much to learn. 
It rarely happens that a Coccinellid beetle ranges 
far from its normal food or a very closely allied species, 
and however flexible and adaptable it may be in rela- 
tion to its normal prey, it generally fails when pitted 
against an unknown or new form. The San Jose or 
pernicious scale is a rather close ally of several of our 
native armored scales, and the Coccinellids that feed 
upon these also attack this introduced form; but east 
of the Rocky Mountains none of them exercise the 
least real control over it. On the Pacific Coast the 
Chilocorus hivulnerus or twice-stabbed ladybird does 
act as an effective check because, having several broods 
during the season, it becomes plentiful enough to de- 
vour a large percentage of the hibernating forms. In 
the east this same species has only a single brood and 
is absolutely impotent. And when we brought in the 
closely allied Asiatic Chilocorus similis to help us out, 
that flourished for a year or two in one of our southern 
states and then died off. In the more northern states 
it never gained a foothold at all. The little Smilia 
misella, native to the Atlantic states, becomes plenti- 
ful enough at times, and may be found feeding even in 
midwinter; but while it undoubtedly helps to keep 
down numbers somewhat, it cannot be considered an 
effective enemy. 



THEIR RELATION TO EACH OTHER 107 

And so we have in these CoccinelUd beetles a series 
of the most highly important checks to some of the 
most destructive insect types, the removal of which 
would cause a serious derangement of conditions as 




Fig. 49. — Chilocoriis sumhs. a beetle laying egg under scale; b, c scales 
awing egg in place; d. egg m scale, e. egg. /, eggs under bark flap, g, same, 
tural size; /z, j, young larvae, ;, same feedmg. 



show 
natura 



they at present exist. These checks are flexible within 
limits, and automatically, by simply devouring each 
other, restore themselves to inconspicuous numbers 
when their services are no longer needed. But we are 
not yet in position to train them to our service nor to 
induce them to feed on unfamiliar species. 



io8 



INSECTS 



In the family Lampyridcc, containing the fire-flies 
and soldier beetles, and among the flower beetles of 
the families MalachidcB and Cleridce, we have a series 
of species of which a large number are predatory in 
the larval stages, while the adults are feeders on pollen 
or vegetable tissue. Among the fire-flies some of the 
larvae are feeders on snails, while others, with those 
of the soldier beetles, are limited to an insect diet. 
They are largely found on the surface of the ground 
or just beneath it, and they get a great many of the 
plant-feeding forms that go underground to pupate. 
Withal they are rather gen- 
eral feeders and not specific 
checks. Among the CleridcB 
the majority of the species 
are predatory on wood-boring 
forms, and some of them are 
specific checks on the bark- 
boring Scolytids. The larvae 
are elongate, rather slender 
and flattened creatures with 
a large head and prominent jaws, and they enter 
into and follow the galleries of their prey, which is un- 
able to escape and absolutely incapable of resistance. 
Under normal conditions these species are capable 
of dealing with a large percentage of the wood-borers; 
but it seems rather easy to turn the scale against them, 
and the Scolytids often do a great deal of injury when 
favored by careless forest practice, fire injury or other 
checks to tree development. Taken as a whole the pred- 
atory and semiparasitic forms among the beetles are 
a very important factor in keeping down plant-feeding 
forms and in preventing the undue increase of other 
species which are not directly harmful and may even 
be beneficial. 




-A soldier beetle 
its larva. 



THEIR RELATION TO EACH OTHER 109 

The order Lepidoptera contains no parasites and 
very few species which, in the larval stage, are preda- 
tory. In the adult stage the mouth structure of butter- 
flies and moths precludes their feeding on other than 
liquid food where they feed at all. A very few of the 
larvae or caterpillars are predatory, feeding on scale 
insects or plant lice. Generally speaking these insect- 
feeding caterpillars are rare; but that of the little 
Phycitid Lcetilia coccidivora is really a very effective 
control for certain of the soft scales. It is a species 
that belongs to the same series as the flour moths and 
meal moths, making the same sort of silken tube as a 
home; onlv, instead of webbing together kernels of 
wheat, etc., it spins up a mass of scales and feeds upon 
the eggs or young even before thev have issued from 
beneath the mother body. 

In the order Diptera we have a very interesting 
mixture of forms, including manv that are of the high- 
est importance as parasitic or predatory checks to 
other species; btit we are less able to limit these species 
to certain families. Here we may have, in apparent 
close relation, species that as larvae are plant feeders, 
scavengers and true parasites; and there is nothing 
in the adult which indicates the habit of the larva, 
so far as our sttidies have yet carried us. Even in the 
midges, which are certainly to be ranked as plant 
feeders, there are a few that have been credited with 
feeding on certain of the smaller plant lice. Among 
the Cidicidcv or mosquitoes there are a number of larvae 
that are truly predaceous, and a few of them, like those 
of Psorophora, arc veritable wolves among the other 
wrigglers. They have the same fault that I have 
already deplored for other species: — they limit their own 
increase by feeding upon their brethren when other 
wrigglers have given out. 



INSECTS 



The blood-sucking flies are considered in another 
chapter and have no important relation to other in- 
sects, although some of the larvae, notably those of 
the Tabanidce, or horse-flies, live to some extent on 
other insect larvae inhabiting swampy and marshy 
soil. The robber flies of the family Asilidce are veritable 
falcons of the insect world and capture their prey by 
pouncing upon it in flight, sucking its juices by means 
of their powerful battery of lancets, and then discard- 
ing the drv husk. They are not at all particular as to 
what sort of species comes 
into their way, — a fly, a bee, 
a beetle or a butterfly, — any- 
thing answers. And so while 
they devour an enormous 
number of specimens, they are 
not specific checks to any line 
of plant feeders. Indeed, as a 
matter of fact the robber flies 
do not discriminate in the 
least: they will as cheerfully 
devour a dragon fly or a 
ground beetle as a butterfly or 
June-bug; it is all a matter of which comes along first. 
Among the bee-flies or Bombyliidcc, we find in the 
larvae both parasitic and predatory types, and forms 
which, like the blister beetles, devour the stored ma- 
terial of bees and other species. The adult flies them- 
selves are often bright colored and hairy, some of them 
resembling bumble-bees in appearance and some with 
long, bee-like mouth parts. In the larval stage some 
are true parasites on caterpillars, notably cut- worms, 
while others feed in the egg-pods of grasshoppers, 
devouring all the eggs in a single pod in attaining full 
growth. Those that feed on the stored food in bee 




Fig. 5 1 . — A robber fly, with larva 
and pupa. 



THEIR RELATION TO EACH OTHER m 

cells are cuckoos in habit and arc effective in limiting 
bee increase. As parasites they are ixOt of so much 
importance, for while they do their share in limiting 
numbers under normal conditions, they do not readily 
increase in abundance when the host becomes un- 
usually plentiful. Of much greater importance are 
those species that depend upon grasshoppers; for 
these do really aid in effective control, the larvae in- 
creasing in relative numbers as the egg-pods themselves 




S^. — A bee-iiy and its pupa. 



become plentiful. There are other predatory larvas 
among the Empidcc or dance flies and similar small 
families; but none of any great importance, until we 
reach the SyrphidcB or flower flies. Among these we 
find a large number that are specific feeders on plant 
lice and among their important checks. 

In this connection it is interesting to note that in 
every order in which there are predatory insects at 
all, there are some that feed largely or exclusively on 
plant lice. We will also find, in another connection, 
that these same plant lice are also seriously influenced 



112 INSECTS 

by diseases and weather conditions, and yet, in spite 
of all these factors, some species escape from their 
checks almost annually to the greater or less detriment 
of the plant hosts. And they always maintain them- 
selves as against all these combined checks even when 
each exercises its maximum influence. It is easily 
appreciable, therefore, that when one or two of these 
factors fail, e.g., weather and diseases, as not infre- 
quently happens, it demands a great increase on the 
part of the other checks to prevent the Aphids from 




Fig. 53.— a Syrphid fly. Mesograpta poiita. 

getting out of hand altogether. The Coccinellid beetles 
have been already referred to in this connection and 
the larvae of the Syrphid flies make a very good second. 
The flies lay their eggs in the very midst of the lice and 
the resulting larva, which is a slug-like creature with- 
out legs and with a very extensile anterior portion 
of the body, begins feeding at once on the specimen 
nearest at hand. This feeding is interesting, for the 
larva fixes the little hooks that serve it as jaws into 
the body of the louse, lifts it high in the air, and holds 
it thus helpless, until the juices have been completely 
extracted. As each of these slugs feeds almost con- 
tinuously from ten days to three weeks, it gains grad- 



THEIR RELATION TO EACH OTHER 



113 



ually even on the plant lice surrounding it, and not only 
checks increase but lessens infestation. Not all the 
Syrphid flies are carnivorous, however; quite a num- 
ber are scavengers, some are pollen feeders and others 
live in the tissues of succulent leaves or stems. 

The really important parasitic group is found among 
the Tachinid flies and their close allies resembling 
house-flies, blow-flies, flesh-flies and others of that 
character. Some of them — the majority indeed — are 
inconspicuous grayish flies of moderate size ; others are 
metallic blue or 
green, with or with- 
out stripes, more or 




Fig. 54. — Syrphus 
larva eating plant 
louse. 



Fig. 55. — A Tachinid fly: its eggs on body of 
caterpillar, larva and pupa. 



less spiny, while a few are large, set with long bristles 
and marked with contrasting colors, appearing formi- 
dable and dangerous, even if they are not actually so. 

These flies lay their eggs on a variety of insects, 
but more frequently on caterpillars, and may be said 
to be specific checks to a great variety of cut-worms, 
including the army-worm. The eggs are often laid on 
the outside of the caterpillars just back of the head 
where the insect cannot reach them, and as they are 
white and of good size, they are easily seen. These 
Tachinids come nearer to being able to keep up with 
the increase of their hosts than almost any other forms 
that I know, and I have on several occasions seen army- 



114 INSECTS 

worms on the march, almost every one of them with 
the seeds of death conspicuously placed upon them. 
Out of hundreds of pupae gathered where armies had 
been feeding, only single examples of moths were ob- 
tained. 

And in this connection we might note that a check 
to the further increase of any plant-feeding species 
does not necessarily mean an immediate cessation of 
injury. Indeed in the armies of parasitized caterpillars, 
every one fed until it was fully grown, and so far as 
injury to the crop was concerned, it made not an ounce 
of difference to the owner of the grain. And so we 
must realize clearly that all these natural checks are 
not imposed to prevent the plant-feeding insects from 
injuring the farmer's crop, but simply to prevent undue 
increase in relation to the surroundings and to preserve 
the balance of nature. 

Yet these Tachinid flies are among the most effec- 
tive engines of destruction to the species which they 
infest. They develop quickly, the females lay a large 
number of eggs and they are themselves not seriously 
affected by secondary parasites. They are therefore 
able to maintain their relative proportion to their host 
no matter how rapidly that multiplies because of the 
removal of other checks. 

Not all Tachinids lay their eggs directly on the 
body of the host. It has recently been demonstrated 
by a series of most interesting observations made in 
the course of the gypsy moth work in Massachusetts, 
that some species lay very small eggs on the leaves of 
infested trees and that these eggs, eaten by the cater- 
pillar with the leaf tissue, hatch when they get into 
the stomach and bore through the walls into the body 
cavity. Yet other forms lay their eggs on leaves, on 
which caterpillars are feeding, fastening each to the 



THEIR RELATION TO EACH OTHER 115 

surface by a little capsule which serves to hold the 
active young larva that hatches almost as soon as the 
egg is laid. Sooner or later the feeding caterpillar ' 
comes within range of this waiting maggot and then 
with a dart the parasite hooks into the skin of its host, 
is torn from the capsule attached to the leaf and bores 
its way in. It will be readily appreciated that this 
plan of scattering the numerous minute eggs over the 
foliage on which caterpillars are feeding is likely to 
reach the hosts in proportion to their abundance. 
If, for instance, a brood of gypsies completely strips 
a tree, every Tachinid egg on it will also get into the 
caterpillar stomachs to the undoing of a vast percentage 
of them. It seems like a hap-hazard way of doing 
things and, no doubt, when caterpillars are scarce, 
very few of the thousands of Tachinid eggs ever find 
their way into any appropriate host. 

It is in the order Hymenoptera, including the bees, 
wasps, ants and the like, that we find the most inter- 
esting specializations in the way of predaceous and 
parasitic habits; specializations so numerous and 
interesting that they demand volumes for their proper 
presentation and can be only referred to here. 

First of all, there is that enormous series of solitary 
wasps, including the mud- wasps, digger-wasps, wood- 
wasps and whatever other modifications of the term 
may be employed; all of which make cells of some 
kind cither in the ground, in pithy stalks, against an 
angle, in a crevice or even attached to a twig, and these 
cells are stored with food enough to bring the larva to 
maturity. Most of the wasp larvae are helpless, foot- 
less creatures, absolutely incapable of seeking their 
own food, and they depend altogether upon the store 
that has been gathered by the parent, and that store 
consists largely of insects or spiders, which are par- 



ii6 



INSECTS 



alyzed by stinging the nerve-centres and then retain 
life enough to remain without decaying until the wasp 
larva has reached maturity. One of the commonest 
examples of this sort is seen in the shapeless cell made 
by our blue mud-wasps under porches, between the 
slats of shutters, under the eaves or even in garrets. 
If we open one of these cells in summer we find it stored 
with small motionless caterpillars or spiders, and either 
an egg or an actively feeding wasp larva among them. 








Fig. 56. — A potter-wasp, Eumcnes fratcrna, at a. its cell b broken open at c, to 
show stored caterpillars. 



On the same order, but much more neatly built, are 
the mud cells of the potter- wasps, which we find fre- 
quently attached to low bushes. These are usually 
filled with small caterpillars, all very much of a size, 
and so closely packed as to fill the cell completely. 
As every one of these cells requires from ten to twenty 
larvae to fill it and a single wasp makes a dozen or more 
cells, the number of specimens thus used up becomes 
quite a factor. Not all wasps feed on caterpillars; in- 
deed, there is scarcely an order that is not fed upon. 
Some digger-wasps fill their cells with grasshoppers; 
others, that make their cells in the hollow shoots of 



THEIR RELATION TO EACH OTHER 



117 



pithy plants, collect plant lice, the larvae of small beetles, 
flies, or even other Hymenoptera. There is hardly a 
species so small as not to be attractive to some of the 
smaller wasps, and on the other hand, the largest Cicada 
or tarantula is not safe from these formidable enemies. 
When large species are fed upon, a single specimen 
often serves to bring a larva to maturitv. The " taran- 



'-^ 




Fig. 57. — Sphecius speciosus carrying a cicada to its home. 



tula hawk," when it has succeeded in finding a suitable 
spider, and has succeeded in quieting it with the formi- 
dable sting, buries its prey and lays a single egg on it. 
We have quite a number of wasps that do little more 
than bury their host and lay an egg on it. The hand- 
some large Sphecius that preys on the Cicadas or dog- 
day harvest-flies, makes a burrow with several laterals, 
in each of which it stores a specimen or two which 
serve to bring to maturity one of the wasp larvae. 
There is an exotic species living on one of the large 
roaches, which, after stinging its prey so as to deprive 



ii8 INSECTS 

it of voluntary motion, is said to seize it by an antenna 
and lead it into a sheltered spot before it deposits the 
egg. The roach simply stays where it was led until 
the wasp larva kills it by feeding. 

This method of stupefying prey is a very high 
specialization and the stinging is by no means a hap- 
hazard one. The wasp seeks the thoracic ganglion of 
the nervous system of adult insects, and may sting' 
several ganglia in caterpillars, to make them entirely 
quiet. The poison introduced is said to resemble formic 
acid in composition and to act as a preservative as well 
as a paralyzing agent. But this preservative effect 
has been disputed and there are yet many interesting 
points to be elucidated in the biology of these predatory 
wasps. The number of specimens collected and stored 
by them is very little appreciated, but it is enormous, 
and the reduction in the number of specimens thus 
preyed upon forms a very important factor in the 
check to undue increase. 

The social or paper-making wasps are also feeders 
upon insects; but not so exclusively, and they make 
no store of food for their larvae. They feed the young 
from day to day with prepared food, chewed into proper 
condition by the nurses, and consisting partly of insect 
fragments and partly of plant juices. 

Ants destroy many insects, but do not usually 
make specific war upon any one species. They are 
very apt to attack, kill and eat almost any sort of 
helpless creature that they find, but few of the species 
of the temperate zone feed largely enough upon insect 
food to form a notable check to any species. 

Several families are exclusively or almost exclu- 
sively parasitic, and these range in size from forms 
so small as to be scarcely visible to the untrained eye, 
to specimens expanding two inches or more, with ovi- 



THEIR RELATION TO EACH OTHER 



119 



positors four or five inches long. Very often, espeeially 
among the smaller species, the colors are brilliantly 
metallic, and they range all the way from smoothly 
shining to deeply pitted as to surface. 

There is no species so small and none so well con- 
cealed in feeding as to save it from parasites, and 
these latter may infest any stage from the egg to the 
adult. It is not unusual to find a batch of "bug" 
(Hemipterous) eggs and to hatch from them a brood of 
minute wasps instead of the little bugs that were ex- 
pected. And when a lot of pupae or chrysalids have 




Fig. 58. — Aphelinus, parasite on armored scales. 



been collected, the result may be butterflies or moths, 
but is just as likely to be several hundred or only a 
few parasites instead. The size of the chrysalis is 
no indication of the number of parasites to be expected. 
Out of a large Papilio or swallow-tail we may get a 
single large Tragus and out of a small Pieris or cabbage 
butterfly we may get one hundred or more little bronze 
Chalcids. On a twig infested by scales one may often 
see a large percentage with little round holes through 
the shell — proof positive that from each a minute 
little wasp has issued; and on a leaf infested by plant 
lice, we often see some that are abnormally swollen or 
rounded and tending to turn gray. These also are 
parasitized and will shortly show a nice little round 




I20 INSECTS 

hole through an empty skin as a reminder of the tragedy. 
Such parasites not only kill the individual, but at once 
stop all reproduction, so that every infested louse is 
at once eliminated as a factor in the increase of the 
species. 

There are several families of these parasitic wasp- 
lets; there is an enormous number of species, often of 
the most bizarre type of structure and with extreme 
diversity in habits. Some species remain within the 
body of their host until they emerge as adults, often 
giving no indication of infestation; others, when fully 
grown, bore out through the skin and form little white 
cocoons on the surface. Some 
of the large Sphinx caterpillars 
or horn-worms are often cov- 
ered with so many of these 
Fig. 59.— Sphinx caterpillar little cocoons as to make them 

covered with cocoons of para- . . . ^ a i 

sites. conspicuous objects. And 

not infrequently the farmer or 
gardener carefully destroys these particular specimens, 
because, in his opinion, they are covered with eggs — 
forgetting the fact that a caterpillar is incapable of re- 
production until it has first become a butterfly or moth. 

A few species, usually those feeding on borers, are 
external feeders, the parasitic larva clinging to the 
outside of its host and sucking its juices through a 
small opening in the skin. 

Some parasites proclaim their character by an ex- 
ternal protruding ovipositor or egg-laying tube, while 
others have it modified into a sting-like organ. The 
sting throughout the Hymenoptera is nothing more 
than a modified ovipositor, and that explains why 
only females of bees, wasps, ants, etc., have it. When 
the ovipositor is external and extended, it varies greatly 
in length. Sometimes it is short and rigid, almost 



THEIR RELATION TO EACH OTHER 121 

like a little borer, at others it is long, slender and flex- 
ible, like a hair or bristle. Many of these elongated 
types are found among species that attack boring 
insects and some are quite capable of piercing deeply 
into woody tissues. Excellent examples of this type 
are found in the species of Thalessa, which expand 
nearly two inches and have ovipositors almost or quite 
four inches in length. These are parasitic on boring 




Fig. 60. — Pimpla conquisitor; a common parasite, with its lar\'a and pup 



larvce of the genus Tremex which live in burrows in 
the trunks of maple and other trees. In some way 
these huge parasites seem able to recognize infested 
trees and to locate, at least approximately, the bur- 
rows in which the borers are working. Then the long 
ovipositor comes into play, and by a unique mechanical 
contrivance the slender, bristle-like structure is forced 
into the solid wood for sometimes its full length before 
the desired burrow is reached and an egg can be de- 
posited. It would be asking too much that the ovi- 
positor should hit the exact point where the borer 



122 INSECTS 

happens to be at the time, and when the parasitic egg 
is once in the gallery, the mother insect has done her 
work. The young larva that hatches in the burrow 
makes its way along until it finds its prey, attaches 
itself, and calmly enjoys life at the expense of its host. 
But the mother insect is by no means infallible, and 
sometimes her ovipositor fails to hit a boring, either 
because it is too deeply located or because it has been 
missed by bad judgment; then nothing remains but 
to try over again. Sometimes, in a vigorously growing 
tree, the sappy wood grips the ovipositor and holds so 
tightly that it cannot be moved one way or the other. 
Every one who has ever tried sawing through a green 
log knows what sort of grip such wood may have, and 
the unfortunate Thalessa that is caught in that way 
is doomed — usually to be picked off by some inquisitive 
bird, sometimes to die of over-exertion. I have several 
times tried to draw out ovipositors caught in that way 
and have never succeeded: the ovipositor always 
broke under the strain put upon it. 

Maturing as quickly as many of them do, they are 
able, as a rule, to keep up with any unusual increase 
of their host, and to enable them to do this even more 
effectively, some species have developed the remark- 
able ability of producing a large number of specimens 
from one egg — polyembryony, as it is called. One of 
these minute species finds, for instance, a butterfly egg, 
and in that lays its own egg, so minute in size as not 
to interfere with the normal development of the cater- 
pillar which hatches in due time, but with that parasite 
egg within its body. The caterpillar grows and so does 
the parasite; but instead of forming a larva and grow- 
ing normally, this parasitic egg forms a structure which 
divides and subdivides and gives off segments almost 
like those of a tape-worm. Each of these segments 



THEIR RELATION TO EACH OTHER 



123 



forms a larva which develops as the host develops 
and finally, when the latter is full grown, it is filled 
with minute, maggot-like grubs ready to form pupa 
cases which will fill the caterpillar skin so completely 
that it seems ready to burst. From a single parasite 
egg, we may thus get fifty 
or more adults; but they 
will all be of one sex as 
determined by the egg 
originally laid. It will be 
readily seen what enor- 
mous reproductive powers 
some of these minute spec- 
imens really have, for even 
if each laid only ten eggs 
and each egg produced 
fifty adults, the progeny 
would still number 500: 
not at all bad for such 
small creatures ! 

With such enormous 
powers of reproduction, it 
seems surprising that the 
hosts are not completely 
exterminated; and yet as 
we know, they are not. 
If we collect chrysalids of 

cabbage butterflies in spring, the chances are that out 
of one hundred we may get ten butterflies and several 
thousand parasites; more than enough it would seem to 
overpower the next brood of caterpillars completely. 
But now, if we collect full-grown caterpillars from the 
scant lot produced by the few spring butterflies, we are 
likely to get a butterfly from every caterpillar. From 
the second brood we are likely to get almost as clean a 




Fig. 6r. — a. Listomastix parasite 
laying a single egg in the egg of a moth ; 
b. the full-grown caterpillar with par- 
asitic cocoons from the single egg. 
After Marchal. 



124 INSECTS 

record, and then butterflies become so plentiful that the 
last brood of caterpillars plays havoc in our cabbage 
fields. By this time the parasites are in evidence again, 
and the hibernating chrysalids are as badly infested as 
they were the year before. The parasite has accom- 
plished its full purpose, the butterflies are not conspicu- 
ously more abundant than they were the spring before; 
but throughout the summer the farmer's cabbage has 
paid the bill imposed by nature's methods. 

There is yet another factor in this connection, 
and that is the matter of what is known as hyper- 
parasitism, i.e., a parasite on a parasite. Not only do 
these parasites infest predatory forms in other orders, 
as for instance the larvae and even adult ladybird 
beetles, but they infest primary parasites among the 
Diptera and in the Hymenoptera, very materially re- 
ducing their effectiveness as checks from the human 
standpoint, but serving an important part in preserving 
nature's balance and preventing the extermination of 
the primary host. The terrific extent of this secondary 
parasitism can best be illustrated by recording a 
personal experience. I sorted out of a collection of 
cocoons of the Cecropia moth 295 specimens that 
were obviously parasitized. Of these seventy -six 
specimens were infested by Ophion containing only a 
single example to each cocoon ; the others con- 
tained species of Spilochalcis and Spilocryptus, each 
cocoon with a mass of at least twenty examples. Out 
of these I bred nineteen specimens of Ophion, the 
others dying of disease, fifty-one specimens of Spilo- 
chalcis and 126 specimens of Spilocryptus: but in ad- 
dition I also bred nearly 50,000 specimens of Dihrachis, 
a secondary parasite upon the two primaries! And the 
matter goes even further: for besides secondary par- 
asites we may have others infesting these, or tertiary 



THEIR RELATION TO EACH OTHER 125 

parasites, checking in turn too great a reduction among 
the primaries. 

It is a merry war in which all these organisms are 
engaged, each one aiming only at food for itself and 
its progeny, and yet each playing its part in that game 
of life in which man seems to be the only one capable 
of appreciating the conditions, though he is himself 
involved and a sufferer as well as a factor in the game. 

It is a pleasure to be able to say that the relation 
of active hostility is not the only one existing between 
insects. Between some there is at least toleration; 
as between others an active friendship based on mutual 
advantage; in a few cases there is almost absolute 
dependence. 

The first case of this kind that comes to mind is the 
relation of certain ants to certain plant lice, and assuredly 
we have nothing in the range of insect behavior that 
exceeds in interest this cultivation or fostering of a 
creature so far different, until we get it in the relation 
of the human being to his domestic animals. The 
relation is even closer, because so much has the lapse 
of time acted upon this interdependence that, while 
the elimination of the plant louse might make little 
difference to the ant. the elimination of the ant would, 
in many cases, mean the destruction of the plant louse. 

It is not possible in this connection to do more than 
mention the fact that among the social insects there 
are a number of different castes and forms, each of w^hich 
has its ow^n function in the community. That is a mat- 
ter of internal administration and is regulated by each 
species in accordance with the conditions which have 
been developed by the stress of the surroundings. It 
is a little different when the matter of slavery comes 
to be considered; when we find that certain species 
of ants actually make war upon weaker forms to obtain 



126 INSECTS 

servants to do their work; and yet even this is a matter 
of domestic economy to be covered rather by a 
student who, Hke Dr. WilHam Morton Wheeler, has 
studied the ants in their relation to each other, than 
by a general work, dealing rather with the relations 
of different kinds of insects. 

In the domestic economy of ants, we have to con- 
sider those species which are of use to the ants them- 
selves and are fostered and cultivated for that reason, 
and those that maintain themselves in the nests in 
spite of opposition or by toleration only. The first 
series are those from which the ants derive a direct 
benefit; the others are those which do them no direct 
harm and rather indirectly benefit them. 

Perhaps plant hce are the best known of those 
that are directly fostered, and they are favored because 
of the saccharine secretion or "honey" which they 
produce. The simplest form of this relation is where ants 
visit colonies of plant lice on vegetation and, by stim- 
ulating or irritating the specimens with their antennee, 
induce them to eject a drop of the sweet secretion which 
is then gathered up. In return the ants attack and 
drive off a great many enemies that would otherwise 
destroy their herds. The next stage is when ants 
build galleries around roots infested by plant lice and 
directly favor them by freeing from soil and other in- 
cimibrances an abundance of feeding surface. This 
would seem to give the plant lice a free field for increase ; 
but not only do parasites find their way into the nests 
but even larvae of ladybird beetles occur in consider- 
able numbers. These latter, however, in almost every 
case, produce from specialized glandular structures, 
waxy fibres which seem almost or quite as attractive 
to the ants as the secretions of- the plant hce. They 
therefore feed upon these processes or rather excre- 



THEIR RELATION TO EACH OTHER 127 

tions, and appear to forgive the intruders their tres- 
passes against the Aphids. A still further special- 
ization, decidedly more important from the economic 
standpoint, is found among those ants that gather and 
preserve the eggs of plant lice during the fall and winter, 
and colonize them on suitable food plants in the spring. 
The strawberry louse and corn-root louse are examples 
of this kind, and both of these Aphids would find it 
difficult if not impossible to maintain themselves were 
it not for the assistance given by the ants. The economic 
importance of the matter comes in when we consider 
that, except for the ants, it would be easy to starve 
out the Aphids by a mere rotation of crops. In some 
instances, where the plant lice will not live under- 
ground, the ants build protecting shelters around the 
colonies on their food plants, and thus gain all the 
advantages that other species get from their under- 
ground forms. 

Indirectly, therefore, ants may become decidedly 
injuriotis to a growing crop, even though they do 
not themselves feed upon it, and the best way of 
dealing with an injurious form may be through its 
protecting ant. 

Besides plant lice, scales are often visited and here 
again the protection accorded by ants in the destruc- 
tion of forms inimical to the scales is the return ren- 
dered for the food supply. It has been charged, indeed, 
that the Sciitellista introduced into California to con- 
trol the black scale, has been practically destroyed by 
ants that obtain honey-dew from the scales. Scales, 
however, are never really domesticated like plant lice, 
and while they are of very great importance to some 
ants they are never entirely dependent upon them for 
existence. Some few species among the tree-hoppers 
and frog-hoppers, also excreting honey-dew or waxy 



INSECTS 



matter, are found in the nests or galleries of ants, and 
are at least tolerated if not directly favored. 

Then, as in all great cities, so the large formicaries 
are inhabited by a rabble of scavengers, thieves, mess- 
mates of all kinds, living in friendly or hostile relations 
as the case may be. These are of the most diverse 
characters, from the lowly Thysanuran to the fellow- 
ant of smaller size or dominating type. Over looo 
species of Myrmecophiles, as such species are called, 
have been already listed 
and their habits more or 
less fully studied and there 
is no doubt that there are 
at least as many more. 
Some of these, like a va- 
riety of rove-beetles and 
some other of the Clavi- 
com series, are scavengers, 
living on the decaying par- 
ticles of organic matter 
found in the galleries, and 
may repay the ants by ex- 
cretory substances coming 
from specialized tufts of hair or glandular surfaces. 
These are favored and protected, while others that pay 
nothing for their living usually keep out of the way as 
much as possible. Some few species, belonging to the 
Histeridcr or pill beetles, are positively harmful to the 
colonies, but are so well protected by their shining armor 
of chitin, that the ants can do nothing with them.. It is 
a case of simply enduring what cannot be cured, and 
such intruders must be constantly on their guard not 
to expose leg or antenna when the owners of the nest 
are about. A few caterpillars have been found in for- 
micaries and these feed on the dead leaves in, over, or 




Fig. 62. — Hister species found 
ants' nests. 



THEIR RELATION TO EACH OTHER 129 

about the nests. The ants seem to pay Uttle attention 
to any save a few Lycaenid larvae that have glandular 
structures producing attractive secretions. A few 
species of small crickets and other Orthopiera help to 
swell the list of guests, and several fly larvs occur. 
Some of these inhabitants steal the supplies gathered 
by the owners of the nest, and against these relentless 
war is waged whenever the ants recognize them; but 
there are curiosities in ant intelligence which, in 
some cases, seems to amount to downright stupidity, 
and which prevents them from recognizing the thieves 
in the most vulnerable stage. Perhaps the worst 
thieves in the formicaries of large species are other, 
much smaller ants that run their narrow galleries so 
as to tap the larger tunnels, and when they are de- 
tected stealing disappear into their own streets into 
which the larger form cannot follow. There are also 
direct parasites adapted to live in such communities 
without recognition, but only mere mention can be 
made of these. There is a good deal of human nature 
in an ant city and the history of what takes place in 
such a city has been written most accurately and en- 
tertainingly by Dr. Wheeler, who is on terms of most 
intimate acquaintance with these species. 



CHAPTER V. 

THEIR RELATION TO THE ANIMALS THAT 
FEED ON THEM 

This subject might be dismissed with a very few 
words in the statement that a large number of birds sub- 
sists entirely on insect food, another large number feeds 
on insects during certain seasons or takes them indiffer- 
ently as part of the general diet, and that the same is 
true of certain mammals, reptiles, batrachians and the 
like. Active defence very few insects are able to make 
against any of these enemies, and we may say broadly 
that the number of insects that may be destroyed by ver- 
tebrate enemies is limited only by their appetite and 
their ability to find prey. The only practical defences 
that an insect has, are its ability to escape the notice of 
its pursuer and its enormous fecundity ; points that have 
been elucidated to some extent in a previous chapter. 

So we can say, roughly, that all kinds of insects 
serve as food for some kind of animal. That is not 
strictly true, of course, for there are some that are so 
minute that they are taken only by accident and a few 
others that seem to be so offensive that no animal will 
touch them; but as a general statement it is accurate 
enough. Some birds and animals eat indifferently 
any thing that comes along; others have a very limited 
diet and go outside of their normal range only under 
the pressure of necessity, which is usually spelled 
hunger. Some animals eat what others avoid, e.g., 
hairy caterpillars, and some insects feed so as to be out 
of reach of all save animals especially adapted to find 
them, e.g., borers sought by woodpeckers. 
130 



THEIR RELATION TO ANIMALS 131 

Among animal feeders on insects we may enu- 
merate toads, frogs, snakes, lizards and all their rela- 
tives; the tortoises generally; rats and mice and their 
allies; the shrews and their allies; bats, coons, opossums, 
moles and, to a less extent, the larger camivora. The 
smaller species of the cat and dog tribe eat a large 
number of insects and even bears count them among 
their list of eatables. Fish eat the aquatic species when- 
ever they can get at them, and birds have been already 
referred to. Now, when we realize that the insecti- 
vorcs among the mammals form a very numerous 
and important series, and that the carnivores assist, 
we get at once a formidable list of destroyers against 
which, as already stated, the insects have little defence. 
The matter of protective resemblance of course comes 
in; but that plays really a very subordinate part. 
There is no doubt that many insects resemble their 
surroundings so closely that they are with difficulty 
to be seen; but they can be seen by the trained eye. 
Some species of moths sit openly on the tree trunks 
in city streets and hundreds of passers-by absolutely 
fail to see them; but to the first entomologist that 
comes along they are as obvious as if they had been 
placed there to attract his attention. It would be 
ranking bird and animal senses very low indeed if we 
seriously believed that such resemblances made them 
actually invisible to those who have in hunger the 
best sharpener for the senses that can be imagined. 
That such resemblances do protect from casual ma- 
rauders there is little doubt, and that there is a better 
chance of escape from a casual search than there would 
be were the insects more conspicuous we may assume; 
but that the resemblance is protective to the extent that 
is sometimes claimed is at least open to serious doubt. 

"Playing possum" is a much better protection, 



132 INSECTS 

and is resorted to by many insects. This means that 
when they are disturbed and apprehend danger, the 
specimens draw in legs and feelers, permit themselves 
to drop to the ground and remain absolutely quiescent 
until they believe the danger past. This very habit, 
however, delivers some of the economically important 
species into the hands of their arch-enemy man, who 
spreads a sheet or other catcher beneath a tree or vine, 
jars the infested plant and gathers in the specimens 
which on the white background are conspicuous enough, 
though in sod or on the bare earth they would be 
well-nigh invisible. 

Warning colors and protective mimicry are other 
passive defenses. Warning colors are simply bright 
or contrasting tints that indicate a species unpalatable 
to ordinary animal feeders on insects of that descrip- 
tion. That there are such species there is no doubt, 
for they seem almost entirely safe from predatory foes. 
Their dress expresses the legend "not good to eat" 
and so they are left unharmed. Now one type of pro- 
tective mimicry is found where a species of another 
group or series normally good to eat so closely re- 
sembles this unpalatable form as to be readily mis- 
taken for it, and some of these resemblances are ex- 
tremely close. Another type is when an inoffensive 
insect so closely resembles one that is capable of de- 
fence, that its enemies hesitate to attack. The re- 
semblance of some Sesiid moths and Conopid flies to 
wasps is a case in point. In such instances it is quite 
usual to find that the mimic has some of the same 
tricks of habit as the protected form and this is at 
least as powerful a safeguard as the color alone. 

Now what place do these vertebrate enemies hold 
in the series of checks to insect increase, and how much 
do they benefit man — the farmer and fruit grower? 



THEIR RELATIOX TO ANIMALS 133 

We have here two questions of very great mterest and 
importance and the answer to the one does not by any 
means determine the answer to the other. That all 
these birds and other animals eat untold thousands 
of insects each year is undoubtedly true, and that this 
is an important factor in limiting the number of speci- 
mens, is unquestionable; but compared with the num- 
bers destroyed by disease, by climatic conditions and 
by other insects, the figures are really insignificant. 
It goes without saying that these remarks are based 
on normal, natural conditions, for it is quite possible 
to change the conclusion under control. For instance, 
if I turn a flock of guinea-hens into a field infested 
with grasshoppers, the fate of those hoppers is sealed, 
provided there are guineas enough to eat them. I 
have seen some fields of alfalfa, however, in the foot- 
hills of the Rocky Mountains, where the grasshoppers 
were so numerous that all the guineas within the county 
would make no serious impression on them. 

As to the food of birds we are left in little doubt. 
Many species have been shot in large numbers at all 
seasons and have had the stomach contents carefully 
determined and classified. One striking fact that 
appears from all the lists that have been published, is 
that the large majority of insect feeders among the 
birds pick up anything they can get hold of most easily, 
and that the commonest reasonably palatable forms 
are those most frequently taken. Naturally, though, 
this does not apply to birds fitted for a special diet like 
the woodpeckers. Among the other animals almost 
the same conclusion applies, again making exceptions 
of such creatures as moles and others which are natur- 
ally limited to underground forms or to species occur- 
ring in limited or specialized areas. 

One consequence of this is that a great many eco- 



134 INSECTS 

nomically harmless insects furnish a large percentage 
of the food: ants, flies, fly larvae in excrement and 
similar species. Another is, that a great many posi- 
tively useful insects are taken ; less so those of absolute 
importance to man by reason of their direct contri- 
butions than those indirect friends, the predatory and 
parasitic forms; and spiders may for this purpose be 
counted as useful insects. Furthermore birds do not 
discriminate between insects that are parasitized and 
those that are not. Hence in eating cut-worms there 
is at least an even chance that parasitized forms are 
taken as freely as those not so infested. In eating a 
parasitized specimen the only benefit derived by cut- 
ting short its life is the saving of its food for a few days, 
because it could not have come to the reproductive 
stage anyway; while a positive harm has been done 
in cutting short the parasites which might have de- 
stroyed a hundred cut-worms the season following. 
It is always possible to draw a variety of conclusions 
from a list of insects found in bird stomachs, and that 
generally drawn, to wit, that birds are always of very 
great importance to the farmer and fruit-grower, is 
usually no more warranted than the contrary one that 
birds are of no use whatever. 

There never yet was an apple orchard kept free 
from codling moth by birds no matter how much chance 
the birds had: in fact in neglected old orchards where 
birds and other animals are never disturbed it is rather 
the exception to find a fruit free from insect attack. 
The same is true of the plum curculio. There never 
yet was a field of grain freed of green-fly by birds, nor a 
tree of any kind saved by them from destruction by San 
Jose scale. In many cases woodpeckers do more real in- 
jury to a tree than the larva they get out would have 
done, and the elm in a grove where birds hold undisturbed 



THEIR RELATION TO ANIMALS 



^35 



sway is just as likely to be defoliated by the elm-leaf 
beetle as its fellow in the city streets where the English 
sparrow holds the fort. It is correct to say that as 
against the common pests of the farm, the field, the or- 
chard and the garden, neither birds nor other vertebrate 
animals are of the least practical benefit and that the 
farmer and fruit-grower would as to them be no worse off 
if every insectivorous bird and other animal were killed. 

And yet withal it is not a fair conclusion, to con- 
tend that insectivorous birds and animals do no good. 
They do, no doubt, constitute a very useful and im- 
portant check to many species that would otherwise 
be much more abundant than they are, and a careful 
preservation of every insectivorous bird and animal is 
good policy — even such forms as quail, partridges and 
their allies, which are now guarded at one season simply 
that they may be shot at another. 

It must again be emphasized that birds and other 
animals constitute only one of the checks to insect in- 
crease and, as against climate, disease, parasitic and 
predatory insects, a very minor and insignificant one. 
We must also remember again that for a naturally 
abundant species the abundance was fixed in spite 
of all the natural checks, including birds and animals. 
Now when such an abundant insect becomes destruc- 
tive by reason of undue increase from any cause, the 
very last factor to become important in bringing it 
back to normal conditions is the vertebrate enemy 
list, including birds, because their number and ability 
to consume remains practically a fixed quantity due 
to their slow rate of multiplication. It sounds large 
when we find loo larvae of an elm-leaf beetle in a bird 
stomach and find loo birds to an acre; but when we 
find loo larvae on a dozen leaves and many thousands 
of leaves on a tree, the figures lose in impressiveness. 



136 INSECTS 

It must be realized that under natural conditions in- 
sectivorous animals depend on insects for their con- 
tinued existence, and that when fed to the full, there 
must yet remain enough to supply food for the season 
to come in spite of all other natural checks, as other- 
wise the animals, birds and others, would themselves 
starve to death. I have already pointed out how pecu- 
liarly well some of the parasitic and predatory forms 
are adapted to gain control of a runaway species, and 
it remains to be added that among the effective forms 
that check the undue increase of parasites, are the 
birds and other animals that eat parasites and par- 
asitized insects. 

Now, in spite of the fact that I am convinced that 
all vertebrate animal life, so far as it affects the insects 
that are injurious to our farm crops, is of little real 
benefit to the farmer and fruit-grower, I would not 
for a moment argue in favor of the destruction of any 
form of bird or animal life not absolutely harmful to 
cultivated crops. Birds have their place in preserving 
the balance of nature and any interference with them 
is sure to react unfavorably to the agriculturist by 
increasing his troubles in some direction; and while 
under normal conditions birds may be of little value, 
yet under abnormal conditions which tend to remove 
checks of other kinds, any increase in bird and similar 
enemies would assist in replacing the other checks. 

I would, therefore, rigidly protect every insectivorous 
bird and other animal, including non-venomous snakes 
and toads, and I would also protect every animal that 
feeds upon insects at any time, providing the direct in- 
jury done to crops or other farm products is not at any 
time sufficient to cause appreciable loss to agriculturists. 

I would not hesitate advising the destruction of 
robins, crows, blackbirds or others when actually en- 



THEIR RELATION TO ANIMALS 137 

gaged in feeding on fruit or grain ; but I would absolute- 
ly prohibit their killing at any time as a mere matter of 
sport. I would be in favor of protecting every bird not 
absolutely harmful ; but of no protection whatever to any 
animal merely for the purpose of keeping it to be shot 
at during some specified period by so-called sportsmen. 

I have no point of difference with those who are 
seeking the protection of bird and other animal life. 
I simply wish to record my disagreement with some of 
the reasons and arguments advanced by them, and to 
guard against an exaggerated belief in the value and 
usefulness of our furred and feathered friends. 

Interference with natural conditions by introducing 
new factors does not always turn out well and should 
not be resorted to without a careful preliminary study 
of possible consequences from all points of view. When 
the English sparrow was introduced into North America 
only one point was kept in mind: get something that 
will eat the span-worm, the larva of the geometrid 
moth, Ennomos subsiguaria. The sparrow really did 
accomplish that feat; but is now a greater nuisance 
than the span-worms ever were and is a direct pro- 
tector of certain species which never occur in trouble- 
some numbers outside the region dominated by it. 
The common Tussock or vaporer moth of the east is an 
excellent example of this, and hardly less striking is the 
case of the wood-leopard moth which has not become 
injurious in this country anywhere except in cities and 
towns where the sparrows keep all other birds out. 

Chickens, ducks, geese, and especially turkeys and 
guinea-fowl are great feeders on insect life and may 
sometimes be used practically, and the useful hog 
esteems wire-worms, white grubs and similar creatures 
as tid-bits to be eagerly sought and worthy of con- 
siderable rooting for. 



CHAPTER VI 

THEIR RELATION TO WEATHER AND DISEASES 
THAT AFFECT THEM 

Very few insects occur throughout the world, and 
those that do are usuall" such as have been distributed 
by or have followed in the track of man or his commerce ; 
but there is no portion of our globe where life occurs 
at all, in which insects are not found. In the polar 
regions they are often unpleasantly conspicuous, and 
in the tropics they frequently render life burdensome. 
When the arctic snows begin to melt during the short 
summer and form puddles on the mossy surface, mos- 
quito larvae appear, and even when there is an ice coat- 
ing over the pools at times they maintain themselves 
and come to maturity. Indeed some wrigglers and other 
insects will stand freezing or imbedding in ice, and come 
out none the worse when a warmer temperature thaws 
them into a liquid medium. There are insects, then, 
that survive in one condition or another the extremes 
of arctic cold: there are others that flourish under the 
opposite conditions of tropical heat. Indeed the lux- 
uriant vegetation of the equatorial regions is accom- 
panied by an infinite variety of insect life, a variety so 
great that we have just begun to appreciate it, and 
which will give a field for study to entomologists for 
generations to come. Furthermore, as we have found 
aquatic forms in water at temperatures low enough to 
form ice, so we find others in waters whose temperature 
ranges close to the boiling point. There are some 
regions so arid that neither vegetable nor animal life 
exists in them; but if at any time under the influence 
X38 



THEIR RELATION TO WEATHER 139 

of rain, vegetation appears at all, insects will be found 
on it. And again, some insects occur in midocean 
among masses of seaweed, undergo their transforma- 
tions and develop generation after generation without 
ever coming within reach of land. 

So we find that there is no climate and almost no 
earthly condition in or under which insects do not 
exist; yet, on the other hand, insects are, as a rule, 
extremely sensitive to changes in climatic conditions, 
and some of them succumb easily to any extreme range 
of temperature, even within their native home. Zo- 
ologists have divided the world into faunal regions 
based on cHmate, and have subdivided these into 
smaller regions based on the geographical conforma- 
tion of the country whose fauna is under considera- 
tion; and we have found in our studies that a large 
number of insect species have an extremely restricted 
faunal range. Beyond that range they do not thrive at 
all, and not infrequently, where no natural barrier 
seems to exist, spread nevertheless does not take place. 
The check in such cases is weather in the broad sense 
of that term, or, more accurately, the meteorological 
conditions. The mere fact that any species of insect 
'is regionally distributed usually indicates that any 
climatic condition not normal to such region would 
be fatal to it. An apparent exception occurs when 
insects are confined to one food plant — the occurrence 
of such plant being then a condition precedent lo its 
existence at all. But this is merely shifting factors 
about a little, for usually the climatic conditions deter- 
mine the distribution of the plant and, in consequence, 
really of the insect as well. 

We know that occasionally we have abnormal 
seasons, and sometimes several seasons of the same 
kind may occur in succession. When that happens 



140 INSECTS 

insects may begin a migration beyond their original 
limits and may extend a long distance into adjacent 
territory, only to be destroyed when a recurrence of 
normal weather conditions renders the invaded area 
unfit as a place of habitation. An example of that 
character occurred in 1896 when the Harlequin cabbage 
bug invaded New Jersey and Pennsylvania, its normal 
range not extending north of Maryland along the At- 
lantic coast. But although it was present in that year 
in destructive numbers, it was completely killed off 
during the winter following and has not been found 
in New Jersey since. It is an example of an insect 
rigorously restricted in distribution by chmatic con- 
ditions, although its food plants are widely distributed 
outside of its own faunal limitations. 

But occasionally matters do not terminate as sim- 
ply. It may happen that an insect long confined to 
a definite faunal area may be started on a migration 
along the line of its food plant, and may be found to 
possess sufficient powers of adaptation to continue its 
life under conditions varying materially from those in 
which it started. A striking example of this is found 
in the case of the Sphinx catalpcE which in its caterpillar 
stage feeds only on Catalpa and which, up to a few 
years ago, did not range north of Virginia and Ken- 
tucky, although its food plant extends into New York 
and Pennsylvania. Somewhere about 1897 it began 
to extend northward through Maryland and Delaware 
into Pennsylvania, and year by year it has extended 
that range until it has reached the headwaters of the 
Delaware River, and has extended throughout New- 
Jersey into New York State. And this extension is 
not of a few individuals only; but of a horde, capable 
of causing defoliation and serious injury to the trees 
attacked. At present it seems as if the species had 



THEIR RELATION TO WEATHER 141 

succeeded in establishing itself in a faunal region defi- 
nitely varying from that in which it started; but there 
are indications also that it has reached its limit. 

A yet more striking case is found in the migration 
of the cotton-boll weevil, a species indigenous south of 
the line between Mexico and the United States, which 
began its invasion into our territory somewhere about 
1893 3-^^ has been annually extending its range through 
the cotton-growing states since that time. So great a 
variety of climatic conditions is now represented in 
its distribution, that there seems to be no reason to 
believe that its spread will be checked until it has 
reached the faunal limits of its food plant; although 
that period may be materially retarded by the quaran- 
tine and other regulations now adopted by the cotton- 
growing states. 

These are instances of natural spread from one 
faunal region to one adjacent thereto, along the line 
of the food plant. There are other cases where insects 
have been accidentally introduced on trees, shrubs or 
plants from one country to another, into which it could 
not have spread naturally and where the climatic con- 
ditions in the new home suited the species so much better 
that injury became much more severe as specimens 
became more numerous. An example of this character 
is found in the recent introduction of the "white-fly" 
of the Citrus from Florida to California, where the dry 
climate exempts the insect from certain disease and 
other checks favored by the more humid climate of the 
eastern country. 

Leaving aside for the moment cases where migra- 
tions have been from south to north when, under favor- 
ing conditions insects from mild temperature regions 
extended into normally more rigorous climates, it 
sometimes happens that conditions reverse, and in- 



142 INSECTS 

stead of a higher temperature extending northward, 
a low temperature extends southward. This is rarely 
followed or accompanied by a southward migration, 
but is very frequently attended by a great mortahty 
among the southern insects which are unable to with- 
stand the drop in temperature. Some species, indeed, 
are so sensitive to cold that a drop of io° or even 5" 
below the normal winter temperature causes a serious 
mortality. 

Besides temperature, the amount of moisture has 
a very decided effect on insect life. Some species do 
best in dry weather, others flourish only when there 
is an abundance of moisture, and sometimes a sudden 
change from one condition to another will produce a 
complete change in insect conditions within twenty- 
four hours. Thripids as a rule require dry weather, 
and after a period of drought and heat, the air may 
be full of the little creatures not over an eighth of an 
inch in length and so slender as to be almost invisible. 
A cold rain lasting a few hours may reduce them to 
so small a number as to make them practically undis- 
coverable. Agriculturists sometimes take advantage 
of this pecuHarity by spraying infested plants with cold 
water, and that is really about as satisfactory a method 
of control as we have. 

Every one who observes nature at all, has probably 
noticed that in some seasons insects are much more 
abundant than they are in others, and, more specifi- 
cally, certain kinds may be almost completely absent 
or on the other hand frightfully abundant. Now in 
most cases these differences are largely and in some 
even exclusively due to climatic conditions. There 
is no greater check to insect life than adverse weather, 
and many of the differences in abundance attributed 
to other causes are really due to climate. 



THEIR RELATION TO WEATHER 143 

During a wet spring certain species of plant lice 
may become so abundant as to threaten a given crop, 
with their natural enemies so far in the rear a^ to seem 
hopelessly out of the running. A sudden change to 
hot dry weather will change conditions so radically, 
that within a week the lice arc gone, while ladybird 
larva; and other plant louse destroyers are feeding 
upon each other. 

No kind of insect is more sensitive to weather 
changes than are the Aphids, and few of them are able 
to resist a sudden change of temperature exceeding 
30° in range; but an increase is not nearly so fatal to 
most of them as a sudden drop. By the term sudden 
I mean within an hour or two, because ranges of 30° or 
over within twenty-four hours, are not uncommon in 
most portions of the United States. 

The character of the winter has much to do with 
the abundance of insects during the summer following. 
It is not so much the hard or the mild winter as the 
variable winter that is fatal to insect life. When arf 
insect goes into hibernation in cither larval or adult 
stage it becomes torpid and capable of resisting all 
usual degrees of cold. Even if the cold is long continued 
at its most intense point it makes little difference and, 
in general, we may say that a continuously severe 
winter is favorable to insect life. The insect simply 
remains torpid and no change in condition occurs. On 
the other hand if there are alternations of freezing and 
thawing, the insect may become partially or altogether 
active and again torpid, losing in vitality at every 
change until it dies or reaches spring in such condition 
as to be unable to complete its tranformations or to 
reproduce its kind. Such alternations are particularly 
hard on pupse and on larvae that winter underground 
in cells. A thaw results in softening the ground and 



144 INSECTS 

partially disintegrating the walls of the cell: a heavy 
frost following heaves the surface, and the water in 
the soil in freezing breaks up the cells completely, 
bringing the soil into direct contact with the soft in- 
sects, crushing or otherwise destroying them. 

A variable winter, therefore, is a hard one on insect 
life, and during the summer following certain species 
are likely to be conspicuous by their absence. It is 
such factors as these that tend to limit a fauna; only 
species capable of withstanding their variations being 
capable of continued existence under them. The com- 
mon and widely distributed species are those that 
have become adapted to a wide range of tenipera- 
ture and relative humidity; the others are more lim- 
ited as to the conditions under which they can exist 
and die off in proportionately large numbers when 
conditions are adverse. 

While climatic conditions are important factors in 
limiting both numbers and distribution, they are per- 
haps more effective in limiting distribution, since the 
occurrence of a species within a faunal region presup- 
poses an adaptation to its normal ranges of temperature 
and moisture. A more effective agent in limiting num- 
bers is found in the diseases to which insects are subject, 
and yet the effectiveness of diseases as a check is in 
large part due to climatic conditions, most of them 
developing best or only in moist hot weather. 

Insects suffer severely from epidemic diseases due 
to micro-organisms — fungus and bacterial — and of 
these diseases we know, as yet, comparatively little. Al- 
most every observant individual has seen late in the 
season, attached to a window pane, specimens of the 
common house-fly with abdomen distended and a 
little whitish powder surrounding the points of attach- 
ment. Such flies have been killed by a disease that is 



THEIR RELATION TO WEATHER 145 

contagious and frequently kills large numbers of speci- 
mens. Grasshoppers are often seen dead and dry, on 
top of some stalk of grass or at the tip of some weed, 
and this death also is due to disease. When we break 
up such a grasshopper we find it filled with a powdery 
mass — the spores of the disease that caused death. 
Caterpillars are sometimes found presenting a peculiarly 
limp appearance, and these when touched prove but a 
pasty mass of bacterial organisms. On a cabbage leaf 
infested by plant lice we may almost always find a 
portion that are dull yellowish-brown in color and 
opaque: victims of disease, easily distinguishable from 
the parasitized examples which are more distended 
and somewhat shining or glazed. And so in every 
order, attacking either larvae or adults, there are dis- 
eases that lie in wait for them and carry off large per- 
centages. Some of these diseases have been long known 
and their effectiveness is so great that efforts have been 
made to propagate with the view of using them prac- 
. tically. But it was found that, while some effect was 
always produced, and while some diseases seemed 
equally effective year after year, others acted only when 
weather conditions were just right and were therefore 
unreliable, because these conditions could not be con- 
trolled even though the germs of the disease might be 
supplied. 

The most extensive and most interesting experi- 
ments of this nature were carried on a few year^ ago in 
some of the states of the central west against the chinch- 
bug, which is one of the most serious enemies to grain 
and com culture in those sections. The chinch-bug 
is a sucking insect belonging to the order Hemiptera, 
and therefore cannot be reached by any stomach poison. 
It is killable by certain contact insecticides, but the 
task of spraying the enormous grain and com fields 
10 



146 INSECTS 

of Kansas and other states of that section loomed up 
so large and expensive, that it seemed discouraging. 
In the exhaustive study carried on by a number of 
entomologists, it was noticed that the species was 
subject to certain diseases and that at least one of 
these was often epidemic in character and capable of 
being propagated. The suggestion was therefore made 
that this disease furnished the natural method for 
dealing with the insect, and field experiments seemed 
to bear out the suggestion. The result was the estab- 
lishment of laboratories for the propagation and dis- 
tribution of chinch-bug disease, in almost every state 
subject to chinch-bug attack, and the introduction of the 
disease into every section where the insect occurred in 
sufficient numbers to attract attention. There were 
some wonderfully successful results reported, and fully 
as many absolute failures, and this eventuated in the 
discovery, after much patient observation, that the 
chinch-bug flourished and delighted in dry weather, 
being most active and vigorous in droughty times, 
when the food plants themselves were in the poorest 
condition to withstand attack. In times of moisture 
the bugs were sluggish, inert, and low in vitaHty, while 
the plants, on the other hand, were vigorous and capable 
of out-growing and resisting injury. The disease, on 
its part, would not develop nor spread in dry weather 
when the bugs were most troublesome; but it did 
spread like wild-fire in a wet season when it was least 
needed. As a dependence to check the spread of the 
insects when danger was imminent, the experiment was 
a failure; but the practice was nevertheless a success, 
because the disease has now been introduced every- 
where and is a constant danger to the bugs, reducing 
them to such small numbers during moist seasons that 
in dry seasons there are not enough of them living over 



THEIR RELATION TO WEATHER 147 

to become dangerous. It would now require a series 
of two or three dry seasons in succession to provide 
for a dangerous outbreak. And this seems, in a way, 
to measure our present ability to use diseases as a check 
to insect increase, i.e., we can plant them where they 
will lie dormant and ready to fall upon the insects 
whenever conditions become favorable. Our knowl- 
edge is as yet altogether too rudimentary to enable us 
to predict future possibilities. 

A disease of the grasshopper has been referred to, 
and this has formed a subject for extensive research 
work in South Africa where the migratory forms are 
among the most destructive pests. It was found that 
there is a disease that sometimes appears among the 
flying hordes and destroys enormous numbers of them. 
This disease has been studied, has been propagated on 
culture media, and has been distributed in pure cultures 
with directions as to how swarms may be infected 
through a prepared food. They depend in this instance 
upon infecting bran, meal or a similar material with 
the disease culture, to be exposed where the wingless 
grasshoppers will find and eat it. They thus become 
inoculated with the germs and establish the disease in 
the swarms in which it afterwards spreads naturally. 
The results on these South African forms are said to 
be very satisfactory. The attempts to establish the 
same disease in our American species have not produced 
any marked results as yet. 

Scale insects are quite subject to disease attack, 
especially in climates like that of Florida, where certain 
of the armored scales are kept at harmless numbers by 
fungi. One of these attacked the San Jose or pernicious 
scale when it was introduced into that region, keeping 
it down without much assistance on the part of the 
fruit-growers. Efforts to introduce this disease into 



148 • INSECTS 

Illinois and New Jersey succeeded in so far that it was 
actually established, but proved utterly incapable of 
catching up with the insects during the hot dry spells 
of midsummer when it rested dormant, while the scale 
flourished and multiplied. When rains came, the tem- 
perature fell below that needed by the disease, and we 
found an evident case of climatic limitation. Evi- 
dences of the existence of the disease may even now 
be found in New Jersey in some localities, ten years 
after it was first introduced; but it never yet cleared 
even a single tree of scales! 

This brings up a point of some interest and much 
importance: the length of time during w^hich a dis- 
ease may lie dormant and retain its virulence. On this 
point our information is very scant; but an example 
in illustration may be given. The periodical Cicada, 
or "17-year locust" as it is more popularly known, 
is attacked in the adult condition by a fungus disease 
that attacks the body of the male, destroys the sexual 
organs and causes the abdomen to drop, so that during 
the latter days of a Cicada invasion a large percentage 
of male examples will be found mutilated in this way. 
So far as is known this disease attacks no other insects, 
and for seventeen years it lies dormant, somewhere, 
ready to become active again when a new brood makes 
its appearance. 

Certain kinds of plant lice are always more or less 
attacked by disease, and some show more diseased 
than parasitized specimens at all times. Indeed I am 
inclined to believe that, aside from temperature con- 
ditions, diseases are the most effective of all checks to 
plant lice increase; but so far as I am aware, no at- 
tempts have yet been made to use any of them prac- 
tically. Perhaps I should guard myself here against 
being misunderstood. I am quite aware that some 



THEIR RELATION TO WEATHER 149 

species of plant lice are so heavily parasitized that 
even when they get a good start early in the year, 
their enemies usually overhaul them before they have 
destroyed or even severely injured their host plant; 
nevertheless I am ready to allow my statement to stand 
as an expression of general conditions, applicable to 
the ordinary run of species. 

I have already referred to the fact that caterpillars 
are subject to disease and the check to certain species 
is, I believe, much greater than is generally recognized. 
On that point I made a very interesting study on a 
large series of light cocoons of the Cecropia moth, 
finding that more than two thirds of all the caterpillars 
died of some trouble other than parasites after the 
cocoons had been completed, but before the change 
to pupa had taken place. Others as well as I have 
observed entire broods of caterpillars dying, and one 
of the characteristic attitudes of such diseased cater- 
pillars is that the twig or leaf is clasped by the pro- 
legs along the sides of the body, while the portions 
anterior and posterior to this hang limp and lifeless. 
Eventually the whole thing dries and shrivels up almost 
to a skin. This sort of condition I observed in Massa- 
chusetts in 1907, in territory infested by gypsy and 
brown-tail moths; fully 50 per cent, of all the larvae 
seen showing evidences of disease: and that condition 
existed to a still greater extent in 1906, when a large 
proportion of the caterpillars of the brown-tail moth 
were wiped out of existence. 

This is eminently one of those cases where an ear- 
nest effort should be made to use the disease-producing 
organisms to check increase and spread, and the study 
of the subject has been actually taken up. It is quite 
probable that it will be found that the disease has its 
limitations, and that it requires certain climatic con- 



150 INSECTS 

ditions for its greatest efficiency. But we can, at least, 
follow up the spread of the insects with the disease, 
and by getting the germs into every colony as fast as 
it is established, introduce a check which is ready to 
act when conditions become favorable, and which may, 
in some localities, control it a?jsolutely. 

Only a small number of insects have been specifi- 
cally mentioned as suiTering from disease attack; 
but this does not begin to indicate the actual extent 
to which they suffer, nor the varying character of the 
infestations. And it is not only those species that live 
above ground on trees or foliage that are affected. 
Some of the underground forms like white grubs, wire- 
worms and others are subject to the attacks of growths 
which change the entire insect into a corky mass, giving 
rise in some cases to processes that reach above ground 
as though the grub itself had begun to sprout. The 
extent to which such conditions occur we cannot esti- 
mate because they are mostly out of our view; but we 
do not find them often enough to indicate that they ex- 
ercise any great influence upon the number of examples 
that come to maturity. 

Among aquatic insects diseases also occur, and I 
have frequently lost entire broods of mosquito larvas 
that have been the subject of some trouble which caused 
a cheesy degeneration. 

Every breeder of insects has had some of his cages 
infected with disease germs so that every brood sub- 
sequently introduced died ofif altogether or in large 
part, and the experienced man to whom this happened 
destroyed those cages altogether if he could, or cleaned, 
disinfected and exposed them to the action of the sun 
and air if for any reason keeping them was necessary. 
He realized that, once established, a germ disease was 
extremely difficult to get rid of by any but the most 



THEIR RELATION TO WEATHER 151 

drastic measures. Many years ago the breeders of silk- 
worms in France found their caterpillars dying at such 
a rate as to threaten the very existence of the industry. 
It was a germ disease of course, but nothing was known 
of such things at that time and it afforded an oppor- 
tunity for Pasteur to win renown and to benefit his 
fellows to a degree that few in that or any other country 
have really appreciated. It gave a striking illustration 
of what epidemic disease could do under favorable 
conditions, and it is still suggestive as to possibilities 
when we attempt to reverse the Pasteur objective. 

At the present time many bee-colonies are suffering 
from what is known as "foul-brood," a disease or dis- 
eases of micro-organic origin which carries off enormous 
numbers of specimens annually. The character of the 
organisms causing these diseases is now known and, 
in a general way, the treatment to be adopted, so there 
is nothing at all mysterious except the negligence of 
the bee-keeper who permits the disease to develop un- 
checked in so many instances. It is probably rare that 
an insect once attacked by disease, recovers. In my 
breeding experiences and in field observations I have 
never known of such a case. I have often seen among 
a brood that sickened, one or a very few individuals 
that showed no trace of disease, that fed normally 
and developed naturally ; but I have never seen such 
a larva show signs of the sickness and then resume 
growth; so in a general way these diseases may be con- 
sidered as fatal when they once gain a foothold. 

We have now seen that, while in general there are 
no conditions of climate where insects do not occur, 
yet climatic conditions may and do in many cases 
check not only the distribution but the numbers of 
insects: that while many species are fitted to live under 
widely varying conditions, others are adaptable within 



152 



INSECTS 



very narrow limits only, and succumb readily to vari- 
ations beyond the normal range. 

We have seen also that, not only do insects suffer 
from germ diseases, but that these often assume the 
dimensions of epidemics and form a very important 
factor in nature's scheme of insect control; a factor of 
which we have not yet made the utmost possible use 
in our dealing with the economically important species. 



CHAPTER VII 

THEIR RELATION TO OTHER ANIMALS 

In the course of their development insects have 
estabUshed the closest kind of relations to the rest of 
the animal kingdom, and there is scarcely a vertebrate 
terrestrial animal that is not more or less affected by 
parasites — man not excluded. Some of this parasitism 
is of the most highly specialized character. We have 
somehow come to think of parasites as being simple, 
lowly organized creatures, of very inferior rank, and 
yet a moment's thought will show that there could be 
no parasites of vertebrates until the vertebrates them- 
selves existed, and as the insects long antedated verte- 
bi-ates, parasitism must have come as a specialization 
from an already well-developed organism. 

Nor is such parasitism confined to what we call the 
lower orders, for we find none of it in the Thysanura 
or primitive forms; but its most elaborate development 
occurs in the Diptera, or flies, which are the highest in 
the scale so far as physiological specialization goes. 

As might be supposed, the Heniiptera, gaining their 
food by piercing and sucking, rank well among the 
orders containing animal parasites; indeed, broadly 
speaking, a large percentage of the order is strictly 
parasitic on either plants or animals. The scale insects, 
for instance, are absolutely dependent upon the host 
plants to which they attach themselves, and many of 
them if once removed from their attachment, are help- 
less and die. The plant lice are less strictly parasitic 
and yet the term "lice" is a good one when we compare 
it with the same term used for those suckers that feed 
153 



154 



INSECTS 



on vertebrate blood 
exceedingly simple 



But the parasitism here is of an 
character, and means only the 
adaptation of the external form 
to a life among fur, hair or 
feathers, and the development 
of some sort of structures to 
hold on with. 

Most hairy animals, from the 
little field mouse through all the 
ruminants to man himself, are 
subject to the attacks of sucking 
lice. Now, while man cannot be 
strictly ranged as a hairy animal 
nowadays, some of his anthro- 
poid allies come conveniently 
under such a definition, and the 
few species that infest humanity 
are some of the remaining dis- 
advantages of a former closer 
relationship with ape-like forms. 
That man has been in this com- 
paratively hairless condition for 
a long time is shown by the fact 
that one of his parasites has be- 
come especially adapted to life 
under such conditions, and that 
another has undergone an even 
more profound modification in 
habit since he was a clothed 
animal. 

These sucking lice are, in 
general, small flattened creat- 
ures, gray, whitish or yellowish 
in color, with an elongate oval body or abdomen cov- 
ered with short hair or spines, and a more or less 




Fig. 63. — Mouth parts of a 
sucking louse. 



RELATION TO OTHER ANIMALS 



155 



pointed head from which a pair of slender styles or 
lancets may be protruded. In many cases there is at 
the base of these sucking structures a series of recurved 
hooks or small horny processes, by means of which the 
creature anchors itself in the tissue of its host and sucks 
at its convenience. Such structures are apt to be devel- 
oped in forms infesting animals with rather scant short 
hair, where some method of holding fast is desirable. 
Another development is on the feet, where the tarsal 




body louse of man; b, hog louse; c, head louse of man. 



joints are arranged so as to be opposable to the end 
of the tibia, like a thumb. In this structure an in- 
dividual hair is seized and held so tightly that it may be 
pulled from its socket sooner than the insect from it. 
This type has been called "scansorial" or climbing, 
because the insect moves about by grasping the hair 
nearest to its position and pulling itself along from one 
foothold to another. An extremely pretty illustration 
of this sort is found in the hog louse, and another in 
the crab louse of man. 

By far the greater number of these parasites attach 
their eggs directly to the hair or bristles of their host. 



156 



INSECTS 



and pass their entire life upon it. They are incapable 
of existence away from this host and have no power 
of gaining food from any other source. The young 
are not very different except in size, from the adults, 
and there is no obvious metamorphosis. 

Three species live on man and their distribution 
is coincident with that of humanity. The head louse, 
Pediculus capitis, lives among the longer hair of the 
body, usually confined to the head. Its legs are not 
scansorial, it has the anchoring process at the base of 
the head well-developed, and the 
eggs or "nits" are attached to the 
hair. The crab louse, Phthirius in- 
guinal is, lives among the coarser, less 
abundant hair of the pubic and ax- 
illary regions and in hairy individ- 
uals also on other parts of the body. 
The legs here are scansorial, as of 
necessity they must be to enable the 
insect to maintain itself, and it also 
glues its eggs to the hair among 
which it lives. The body louse, Pediculus vestimenti, 
lives among the thinner body hair and almost alto- 
gether on parts normally covered by clothing. Its legs 
are not well fitted for grasping, but the anchor proc- 
esses of the mouth are well developed. The peculiarity 
of this species is that it remains on the body of the host 
only while it is feeding and at other times hides in his 
clothing, where also it deposits its eggs. Man, there- 
fore, has worn clothing for a period long enough to 
enable this parasite to adapt its mode of life to this 
habit, and to depend upon his garments for protection 
and as a nidus for its ova. 

These parasites sometimes become exceedingly 
abundant when men are herded together in camps, 



Fig. 65. — An egg 01 
nit, attached to a hair. 



RELATION TO OTHER ANIMALS 157 

ships, or prisons, and specific irritations known as 
Pediculosis and Phihiriasis are produced by them. 
It has been calculated that a single adult female of 
the body louse might have, in eight weeks, a progeny 
of 5000, and while this is not equal to the performances 
of some other insects it does, nevertheless, serve to 
make possible a very rapid and complete infestation 
where they are allowed to develop unchecked. 

Of course personal cleanliness is the best of all 
methods to be and become free from such parasitism; 
but infestation in modern conveyances is always pos- 
sible, and with even the greatest care a parasite may 
obtain a foothold. Children, who are not always choice 
in their companions, not infrequently become infested 
by head lice. A fine-tooth comb and a thorough greas- 
ing of the hair with pomade or any fatty material, 
repeated twice at intervals of a week each, will clear 
out the parasites. The grease enters into and clogs 
the breathing pores of' the lice and chokes them; but 
it does not affect the eggs or "nits." The later 
applications are intended to reach the young that 
have hatched from the eggs since the previous ones. 
As the eggs may remain unhatched for ten days or 
two weeks, this period of time will be necessary to 
insure freedom. 

As for the body louse, the infested clothing should 
be discarded for a time. Underclothing may be sub- 
jected to lengthy boiling to kill both adults and eggs. 
Outer garments should be steamed or baked if possible, 
or should be dipped into gasoline; this latter applica- 
tion to be repeated in ten days, to reach later hatchings. 
The gasoline process is simplest as it kills all the adults 
at once, and if it can be repeated at short intervals, 
the clothing can be worn in the periods between 
treatments. 



158 INSECTS 

The crab louse is treated by local applications of 
mercurial ointment or by tincture of larkspur (Del- 
phinium), the latter of which is also used against the 
head louse. 

The habit that some savages have of covering them- 
selves with grease, oil or paint, is not entirely without 
practical advantage, for thereby they do undoubtedly 
keep themselves measurably free from these parasitic 
forms. The use of ants to rid infested clothing of para- 
sites is referred to by Mark Twain in his inimitable 
way, and it was a recognized 
practice in the far west in 
olden days, when changes of 
clothing were not readily ob- 
tainable, and when lodgings 
and lodgers could not be 
chosen but had to be ac- 
cepted as found. It meant 
simply stripping naked, and 
Fig. 66.— Crab louse of man. placing all the clothing on 
an ant hill, where it would 
be immediately invaded by the ants anxious to attack 
and destroy every living thing on or in this foreign 
material. In a short time the clothing could be again 
put on with the comforting assurance that it was at 
least temporarily free. 

Most of our hairy domestic animals are subject to 
the attacks of similar parasites, each of which lives 
and propagates on the body of its respective host. 
Spread from one animal to another occurs when they 
are in contact in stables, or herded closely together for 
shade in the pasture. Sometimes a parasite leaves 
its host voluntarily or is rubbed off by it in the stable, 
kennel or field. It may then crawl about on woodwork, 
plant or tree, hiding in crevices until another host 




RELATION TO OTHER ANIMALS 159 

animal comes into such a position as to enable it to 
crawl among the hair or wool. 

As uncivilized man greases or paints himself, so 
animals have developed a method for securing freedom 
from parasites: they dust themselves or coat them- 
selves with mud. The spiracles of most lice are not well 
protected, so when animals get into a dusty road and 
roll about, this serves a very practical purpose and 
those that get into a mud hole and wallow are often 
seeking similar relief. Other species of Hemiptera 
preying upon man will be considered under the heading 
of household pests. 

Besides the sucking lice belonging to the order 
Hemiptera, many animals and most birds are also sub- 
ject to the attacks of biting lice, belonging to the order 
Mallophaga, which means, literally, wool-eaters, and 
is somewhat misleading. Commonly they are also 
known as "bird-lice" because they very usually infest 
the feathered tribe. In color and appearance they do 
not much differ from the sucking lice; but the head 
is usually more blunt, and instead of puncturing the 
skin and living on blood, they have mouth parts formed 
for chewing and biting, and live rather on the surface 
scales and scurf at the roots of the hair and feathers. 
They do not puncture the skin to reach blood, but will 
feed on clotted blood at the edge of any wound and may 
prevent healing, or even cause the extension of a sore 
spot. And so, while a few individuals on the skin 
cause little inconvenience or unpleasant effect, yet 
when a great number are at work, the feeding at the 
base of the hair and of the smaller feathers results in 
the death of these out-growths and the infested animal 
becomes "mangy" in appearance. The true mange 
is, of course, due to a mite parasite of quite a different 
kind; but that "mange" which consists of bare spots 



i6o INSECTS 

on a hairy animal or thin plumage on a chicken or 
other bird, is very apt to be due to biting hoe. In breed- 
ing habits they resemble the Pediculids very nearly; 
the eggs are fastened to the hair or feathers and there 
is little apparent change in outward appearance from 
the nymph just out of the egg, to the adult ready to 
reproduce. None of these species are found on man ; 
but nearly all farm animals and all the domesticated 
birds are likely to become infested, each with its own. 




A // ' B 

Fig. 67. — a, chicken louse; b, turkey louse. 

peculiar species. It is rare that one species of parasite 
is found on two species of animals not very closely 
allied; but it is not uncommon for a single species of 
animal to harbor two or more kinds of parasites. 

Birds are as fond of a powder bath as are the four- 
footed animals, and poultry keepers have long recog- 
nized the importance of the dust box in keeping their 
charges in good condition. It should always be the 
finest of dust available and there should always be 
plenty of it in a box of generous size so that even the 
largest bird can cover itself thoroughly without scat- 
tering the material beyond the edge of the container. 



RELATION TO OTHER ANIMALS 



i6i 



Horses and cattle can be very readily freed from 
lice parasites by a free use of curry-comb and brush, 
and if occasionally the brush be dipped into a pan of 
crude petroleum so that the tips of the bristles become 
wet, the coat of the animal will be materially improved, 
and any louse that is hit will be killed. Kerosene must not 
be used because that is likely to kill the hair; but crude 
petroleum acts as a stimulant and improves its growth. 

There are no animal parasites in the other Neurop- 
terous orders, and in the great 
order Coleoptera or beetles there 
are very few. We have scaven- 
gers and feeders on dead and de- 
caying material in great abund- 
ance, and many beetles live with 
specific animals in very close re- 
lationship ; but very few actually 
occur on the animals themselves. 
In the United States the mem- 
bers of the family PlatypsyllidcE 
and LeptinidcB are known to live 
on the beaver and a few other ro- 
dents that have a dense fur. 

Just what the relation of these parasites is to the host 
is not entirely clear, but the larvae do not live on it, 
and feed rather on the waste material in the nests. 

Animal parasites would scarcely be expected among 
the order Lepidoptera, or butterflies and moths, and 
strictly speaking there are none. Yet it is certain that 
some of the small moths belonging to the Tineids, 
which include our "clothes moths," do actually breed 
and develop in the fur or wool of animals like the sloth, 
certain sheep, etc. There is such a thing, then, as a 
fur or pelt becoming moth-eaten, even while it still 
covers the body of its owner. 




68. — Platypsylla cas- 
/o-r)5; parasite on beaver. After 
Westwood. 



l62 



INSECTS 



The great order Hymenoptera, in which insect para- 
sitism is developed to a remarkable extent, contains 
no species that live on vertebrate animals. 

The Diptera, or flies, on the other hand, in which 
specialization has been almost as extreme as in the 
Hymenoptera, have developed a considerable number 
of forms that depend for their living entirely upon the 
higher animals. 




Fig. 69. — A rabbit flea. 



The little family of fleas, which are very highly 
specialized flies, although now usually classed in an 
order by themselves, are all parasites on warm-blooded 
animals covered with hair or feathers. They are small, 
brown, transversely flattened, set with spines or stiff 
hair directed backward, and the legs are powerful, 
fitted for jumping. This characteristic form makes it 
very easy for them to move about among the hair and 
feathers, and this they do in a sort of jerky way as if 
they were making short jumps, each of which carries 
them a shorter or longer distance and enables them 



RELATION TO OTHER ANIMALS 



163 



to easily avoid the paw or foot of the animal when it 
scratches the place where it feels a bite. Although 
parasitic in so far as it lives during its adult stage upon 
the host animal, yet the insect moves about freely, 
and the early stages are passed in most if not all cases 
among the litter in the nest or den of the host, and not 
on its body. In its early stages, then, the flea is not a 




Fig. 70 — The jigger flea: a, normal female; b, distended with eggs; c, larva. 



parasite, but rather a scavenger; in its adult stage it 
feeds on blood and differs from mosquitoes and other 
flies that have the same habit, chiefly in remaining on 
the host animal during the period when it is not feed- 
ing. As soon as an animal is dead and cold the fleas 
leave it. Of fleas in their relation to man there will be 
more to say in a later chapter. 

There is one little group of fleas roughly known as 
"jiggers" that depart somewhat from the normal life 
history. In these species the female after copulation 
seeks some host into which it may burrow or imbed 



i64 INSECTS 

itself. Any animal, including man, will serve, and 
entrance is usually made between the toes or under 
toe-nails or claws, because penetration is easiest there. 
When once in position under the skin, the body of the 
female enlarges as the eggs develop until it is as big 
as a pea in an extremely painful and usually festering 
tumor. The eggs, when ready to be laid, are discharged 
into the sore, and the wriggling larvae make their way 
out as best they can, to develop as do others of their 
kind. Animals often suffer severely from the attacks 
of these pests which inhabit the southern parts of our 
country and the tropics, and man is not infrequently 
attacked where he goes bare-footed. Where "jiggers" 
are well known the nature of the attack is usually recog- 
nized at once, and the insect removed with a needle or 
a knife-point; sometimes a wet quid of tobacco is tied 
over the infested spot for a few hours, and this softens 
the skin and usually kills the pest so that removal is 
easy. If the matter is neglected and removal is not 
attempted until the eggs are developed, the work must 
be carefully done so as to avoid breaking the body of 
the female and discharging the eggs into the wound. 
Usually, on domestic animals, cleanliness and the 
free use of lime where the larvae breed is sufificient to 
avoid trouble. But in some sandy regions fowls suffer 
severely from the species that attacks them. The hen 
flea is an ally of the "jigger" and while it does not bore 
into the tissue of the bird, the female does fasten itself 
firmly into the skin and remains attached until dis- 
turbed by some outside force. On young chicks they 
often fasten to the head and neck in such numbers as 
to kill their host. A free use of carbolated vaseline is 
indicated in cases of that kind. This material not only 
kills the fleas but acts as a disinfectant and promotes 
the healins: of the sores. 



RELATION TO OTHER ANIMALS 165 

There are many other kinds of fleas and they infest 
almost every sort of animal capable of affording them 
shelter; but there is a very general agreement in life 
history and in the character of the methods to be used 
in their control when control becomes a matter of im- 
portance. Some further word concerning these insects 
as carriers of disease will be found in a subsequent 
chapter, where also the closer relation of those fleas 
that occasionally occur in our houses is more fully 
elucidated. 




Fig. 71 



Among the true flies there are a great number of 
species that prey upon vertebrate animals, and they 
do this in two ways: either by feeding upon them in 
the adult stage alone, or by actually living upon them 
in early stages, and thus becoming true parasites. As 
the flies are among the most recent of insects, so their 
relations to the vertebrates, the most recent develop- 
ments in the higher animals, are also most close. 

The simplest form of relationship is that afforded 
by the various blood-sucking flies — the mosquitoes, 
gnats, midges, horse-flies, stable flies and others allied 
to them. In all these species the mouth structures 
are developed into a series of long slender lancets 



166 INSECTS 

formed so as to be able to ouncture the skin of the host 
and to suck the blood beneath it. In almost every 
instance the early stages are passed elsewhere than on 
the host that serves as food in the adult stage, and some- 
times not even in the same medium. The mosquitoes, 
for instance, attack all sorts of vertebrates, cold-blooded 
as well as warm-blooded; but so far as known, all the 
larvse are strictly aquatic, dwellers in water and adapted 
to secure their food only in that medium. Yet while 
the direct relations between animals and mosquitoes 
are simple enough, the indirect influence that they 
exert as intermediate hosts for certain disease-produc- 
ing organisms are of so great importance as to require 
more specific treatment in another connection. 

The SimuliidcB, containing those species known as 
"black flies," "midges," "Buffalo gnats" and others 
of similar character, are in somewhat the same case. 
The adults feed on warm-blooded animals, the larvae 
are found only in water usually adhering to stones, 
logs, roots or other points of attachment and gaining 
their food supply entirely from beneath the surface. 
As both mosquitoes and gnats develop in water, their 
presence as adults in some localities is coincident, and 
a better combination for making life miserable can 
scarcely be imagined. The gnats are preferably day 
fliers, the mosquitoes preferably night fliers, so the 
entire diurnal cycle is thus provided for. The "black 
flies" do not worry their victims by buzzing or "sing- 
ing." They are extremely business-like in their method 
and as soon as they alight they set to work. Their 
puncture is recognizable at once and resembles the 
prick of a hot, very fine needle, much more than any 
other bite known to me. The mouth parts are short, 
not nearly so compact as those of the mosquitoes, and 
the flies appear to veritably dig into the skin leaving, 



RELATION TO OTHER ANIMALS 



167 



when driven off, a wound large enough to bleed — a 
butchery of which no mosquito is ever guilty. The 
small black flies, usually called "midges," are not con- 
tent to attack only the exposed parts of the body: 
they crawl into the ears, the nose, under the clothing 
at the ankles, wrists or neck, and where a novice goes 




Buffalo gnat" or "black fly." 



unprepared into an infested territory, he usually stays 
there only as long as is absolutely necessary. Even 
the veteran is sometimes forced to run when he has not 
provided himself with some repellant substance. Of 
these "dopes" there are various sorts known to the 
woodmen, and their basis is tistially a cotton-seed or 
olive oil, with an admixture of oil of tar, oil of penny- 
royal, menthol or some similar volatile oil. Oil of 
citionella is in great favor with many and, in my own 



i68 



INSECTS 



experience is a little the most satisfactory and agree- 
able. The odor is offensive to others, however, and 
these may find the menthol preparations more satis- 
factory. Cattle and animals not being able to resort to 
repellants often suffer cruelly, and in countries where 
buffalo and similar larger gnats are plentiful, they 
are sometimes driven literally insane by the pain and 
irritation of the attack. 

The early stages being 
passed continually under 
the water surface, offer no 
points for an attack with 
oils. No matter how the 
upper layer may be coat- 
ed, the insects on the bot- 
tom will be little or not at 
all disturbed, and as they 
usually inhabit running 
streams, it is practically 
impossible to maintain a 
surface covering anyhow. 
Those species that attach 
themselves to logs and 
sunken or surface-lodged 
tree trunks or the like, may be mitigated by cleaning 
out such obstructions and points of attachment; but 
for such species as attach themselves to stones on the 
bottom we have no remedy that is not also likely to be 
fatal to fish and other forms of aquatic life. Thus far 
no charge has ever been made against any of the 
SimvdiidcB that they are carriers of disease in man or 
animals ; but our actual acquaintance with the flies and 
with the diseases of the animals that inhabit their ter- 
ritory is slight, so that it would hardly be safe to say 
that they are not dangerous in such direction. 




-Larva and pupa of buffalo 
gnat. 



RELATION TO OTHER ANIMALS 



169 



The Tabanidcc, including those forms known as 
"horse-flies," "deer-flies," "green-heads," "breeze-flies," 
"golden-eyed flies, " and perhaps a number of other pop- 
ular term's, are all much larger species, some of them 
among the largest in the order. They are all blood 
suckers in the female and feeders on nectar or other 
plant secretions in the male. In fact the males are 
as shv and retiring as the females are bold and obtru- 




IV) 




Fig. 74. — Black horse-fly. Tabanits atralus: a. larva; b, pupa; c. adult. 



sive, and very little is actually known of them and their 
habits. The popular names are all applied to the fe- 
males and are chiefly based on their habits or appear- 
ance. The "horse-flies" are among the largest of the 
species — some of them great massive fellows an inch 
or more in length; black, blue, brown or striped with 
yellow; sometimes covered with a bluish, whitish or 
golden bloom. They attack horses or cattle in their 
districts and so stout and short are their homy lancets 
that blood comes almost as they settle. High-strung, 
thin-skinned horses are sometimes driven frantic by 



170 INSECTS 

the bites and by the circHng of the flies seeking a place 
to alight, and high-bred cattle fall off seriously in fly- 
infested pastures. 

I have referred to districts in connection with these 
flies and not unintentionally, because they are by no 
means generally distributed. Each species has its 
favorite haunt and cannot be found outside of it; so, 
in driving, one may enter a fly district and get out of it 
again in a few minutes. Or, after being bothered for 
a few minutes by a large black fly, it may be noticed 
that a large brown or striped one has taken its place. 

The "green-heads" are usually found along the 
sea-shore and their name is due to the bright green eyes 
which cover so much of the head that nothing else is 
ordinarily noticed. The rest of the body is generally 
of some light or yellowish shade that is inconspicuous in 
the surroundings in which they occur. 

The "golden-eyes," "deer-" or "breeze-" flies are 
usually inhabitants of damp woods and their names 
are derived partly from the golden brown mottled eyes, 
partly from their supposed habit and partly from their 
manner of attack. These are, as a rule, smaller flies 
and many of them have the wings barred or mottled 
with brown or black. The golden markings of the eyes 
are quite conspicuous, and it has been interestingly 
demonstrated that this is due to a distinct pattern for 
each species and that in life many forms are identifiable 
by this character alone. 

The Tabanid larvae so far as we know them, live in 
mud or at least in moist earth along the banks of streams 
or almost in water itself; and they feed on the minute 
forms of life inhabiting such places. Some occur on 
salt marshes, some in low meadows and some in the 
damp leaf mould in low woods, and this, in a measure, 
accounts for the local distribution of the adults: they 



RELATION TO OTHER ANIMALS 171 

do not get very far away from the place where they 
normally breed. 

As a protection against these insects nettings are 
used on driving horses, and cattle are sometimes pro- 
tected by smears of carbolated grease or fish oil. The 
larger horse-flies do not usually attack man, as the 
green-heads and deer-flies generally do. Where they 
are abundant enough to cause trouble, the same 
repellants that serve for black flies will sei-ve against 
the Tabanids as well As the ground becomes better 
drained or cleared, so that breeding places for the larvae 
are lessened in number, the adults will become gradually 
less troublesome; and, as a matter of fact, while the in- 
sects are sometimes horribly annoying, they are usually 
much fewer than they seem because of their active 
movements, and it may be quite possible to exterminate 
some of the species locally, by persistent collecting on 
some especially favored animal, for a few days after 
the flies first make their appearance. 

The term "stable flies" is rather an indefinite one, 
but applies chiefly to one species, Stomoxys calci trans, 
of very general distribution, in appearance like a large 
house fly, but with mouth parts produced so as to be 
capable of sucking blood. These are often present on 
horses and cattle in great numbers, and frequently 
cause great annoyance and distress. They rarely attack 
humans, but sometimes in hot, oppressive weather 
will get at exposed ankles and bite hard, usually with- 
out causing any noticeable swelling. The larvae are 
maggots, like those of the common house fly, and de- 
velop in excrement, preferably in cow dung. If no better 
lodging is found for them, almost any kind of decaying 
vegetable matter will be made to answer. 

A near ally to this stable fly is a somewhat smaller 
species known as the "horn fly" from its habit of 



172 



INSECTS 



clustering at the base of the horns of cattle. This is 
an importation of comparatively recent date from 
Mediterranean Europe, but it has spread in the few 
years since its arrival throughout most of the United 
States and into Canada. For a few years after its 
first appearance it produced great alarm, and weird 
stories were told of its destructive effect on cattle; 
the least of which was that the flies attacked the horns 




Horn fly: a, egg; 6, adult; c, ci, head and mouth parts. 



at base, laid their eggs there, ate off the root of the 
horn and then penetrated the brain. As a matter of 
fact much injury was caused to dairies from the abund- 
ance of the flies, because they kept the cattle in a con- 
stant state of irritation and therefore poor in milk flow. 
But breeding was always in fresh cow manure, and at 
no time did the insects get within the outer surface of 
the animal in any stage. After two or three years of 
alarm it was noticed that the flies lessened in number, 
and finally became less abundant than the native 
species, which it seemed at first fated to displace. 



RELATION TO OTHER ANIMALS 



173 



Carbolated fish or a similar oil is used as a repcllant, 
where flies of this character are abundant; but proper 
attention to the manure so as to prevent breeding is 
a much more effective and satisfactory measure. 

Leading to those species that have been referred 
to as parasitic because, in the larval stage, they are 
confined to and dependent on the host, are a number of 
species that in a sense are intermediate in habit. There 







Fig. 76. — Screw-worm, Lucilia macdlaria: a, b. 
pupa, e. rty; /, ils head. 



larva and details; d, 



are many species that are true scavengers in the larval 
stage; maggots which are found on exposed meats, 
fish or vegetable matter, and which in an almost in- 
credibly short time dispose of most of the organic matter 
of an animal of even consideraljle size. And in the 
determination of what is suitable organic matter, the 
adult flies of some species seem to follow the rule 
that it is best to "blow" anything that might by any 
chance be suitable. Hence while the parent of the 
"screw-worm" normally lays her eggs in or on dead 
animals or on exposed meats, yet sometimes, when 
suitable food is scarce, she will select any raw or sore 



174 INSECTS 

surface on even a living animal. Most of the flies of 
this series are attracted by foul odors which, to them, 
is an indication of a suitable place for eggs; hence it 
is not altogether unusual to have a female oviposit 
into the open mouth or into the nostrils of a sleeping 
human afflicted with catarrh or some other trouble 
giving rise to foul breath. Eggs of this kind are usually 
ready to hatch when laid and sometimes already hatched 
within the abdomen of the female; hence it is a matter 
of only a very short time for the young larva to make 
its way along the mucous membrane, in which it may 
exist for a day or two without giving rise to much dis- 
comfort. After this it bores into the soft tissue of the 
palate and into the cavities and sinuses of the head, 
giving rise to intense pain, high fever and often death, 
if the character of the trouble has not been at once 
recognized and prompt treatment made. Yet this 
form of parasitism is incidental or accidental, and shows 
principally how slight and easy is the step from the 
beneficial scavenger to the injurious parasite. When 
the eggs are deposited on or near an open wound or 
sore surface, the larvae bore into the exposed tissue and 
feed upon the living flesh, which of course becomes 
much inflamed, ulcerates and attracts yet other flies 
of the same character, unless the matter is promptly 
looked after. The screw-worm flies are common enough 
throughout the middle, southern and central states, 
but are most troublesome in the south and the south- 
west where, during some years, much loss among domes- 
tic animals has resulted from their attacks. The adults 
are stout flies almost two-fifths of an inch long, 
metallic bluish in color, with three blackish longitudinal 
stripes on the upper side of the thorax. 

A very similar but somewhat smaller species is the 
blue-bottle fly, much more common in the northern 



RELATION TO OTHER ANIMALS 175 

states and more metallic yellow or green in color, which 
has similar habits so far as attacking wounds or raw 
surfaces is concerned; but it does not, so far as I am 
aware, ever actually bore into living flesh nor into the 
openings of the face. The nearest approach to this 
was in the case of a tramp admitted to the hospital at 
New Brunswick, complaining of unbearable headache. 
Investigation showed the ear cavities filled with a dirty 




Fig. 77. — Blue-bottle fly, Litcilm carsar. 

mass in which were found maggots which I believe 
were of this species. The ears were cleaned, syringed 
and all the maggots removed before they had pene- 
trated further into the head cavities. 

The large blue "meat-fly" or "blow-fly" has sim- 
ilar habits and seems to occur all over the world, at- 
tracting attention by its large size, deep blue color 
and noisy hum. 

The one guard against all these semiparasitic scav- 
engers is cleanliness and disinfection. It is the attrac- 
tion of foulness that brings them to the attack, and if 
by unavoidable accident an attack is made on some 



176 



INSECTS 



unprotected point, prompt treatment to destroy the 
larvae, reduce inflammation and protect the wound, 
should be resorted to. Carbolated washes or ointments 
are excellent as protectives, and nothing is better than 
peroxide of hydrogen to clean and sterilize a suppur- 
ating sore. 

It is rather an easy step from the sort of elementary 
parasitism just described, to the simpler forms of at- 
tack by bot-flies, or QLstrida. Bot-flies in the adult 
stage are usually large, stout species with a large head, 
but no functional mouth parts. 
% 'atM- / '^^^^ adults, therefore, though 

^^^^ >g very highly specialized in some 

^H|^^ directions, are merely produced 

to provide for the continuance 
of the species ; incapable of harm 
in themselves and, so far as we 
know, not productive of any 
distinct good. 

In the simplest forms the 
adult fly lays an egg on the skin 
of the animal that serves as a 
host; the larva hatches, bores its way through the skin, 
enters the tissue and lodges. It increases in size, some- 
times forms a swelling which may or may not suppurate, 
and, when full grown, works out through the skin, drops 
to the ground which it enters to pupate, develops to an 
adult in due course and the cycle is complete. Bots of 
this character attack a great variety of animals and even 
man is not exempt from them. I have personal knowl- 
edge of such a case and there are Enough others on 
record to make it quite certain that under abnormal 
conditions some of the species that ordinarily attack 
other animals may attack man. In tropical regions the 
attacks on man are much more frequent and are referred 




-Blow-fly, Calliphora 
vomitoria. 



i 



RELATION TO OTHER ANIMALS 



177 



to species of Dermatohia. So far as I am aware no 
species has been demonstrated that is confined to 
human beings. 

Almost any part of the animal body may be at- 
tacked by bots; but in a general way they are most 
likely to appear in regions which the host is least able 
to reach with its teeth, e.g., the neck; but they occur 
often enough in other portions of the body. Occa- 




FiG. 79. — The sheep bot, CEstrus ovis: i. 2, flies; 3, pupa; 4, 5, full-grown 
larvae; 6, young larva. 



sionally they appear to attack specific organs as those 
that destroy the testes of squirrels and chipmunks, or to 
be confined to special regions like those that are so often 
found around the anal openings of hares and rabbits. 

Some species have almost identically the habits that 
were observed in the screw-worms entering the head 
of man through the nostrils. An example of this is 
the well-known sheep bot, the adult of which lays its 
eggs ready to hatch or just hatched on the mucus of 
the nostrils of the sheep. The larvae work their way up 
into the head passages, feeding on the mucus, on the 
12 



1 78 INSECTS 

membrane itself and, if pressed for food, upon the 
muscular tissue. When the infestation is a bad one 
they work their way, through all the openings between 
or in the bones, to all parts of the head cavity, and into 
the brain itself, in such cases causing "staggers" and 
death. The larvae like almost all bots are set with 
short stiff spines, definitely arranged, that enable them 
to make their way forward, and there is also a pair of 
mouth hooks that enables the grub to fasten itself 
firmly to any place selected. This spiny structure and 
the definite mouth hooks are not developed in the 
"screw-worm," which is a typical maggot, altogether 
unlike the highly developed "bot. " The amount of 
damage caused by the sheep bot is very great in many 
localities, while in others the species seems to be alto- 
gether unknown. As to remedies against them, each 
locality or herdsman has its or his own, and none is 
entirely satisfactory. 

An altogether different type of bot is that which 
occurs in horses. The fly that produces this has rather 
a conical pointed abdomen and a brown hairy body. 
The eggs are laid on and attached to the hair, usually 
on the forelegs or on some part easily reached by the 
horse with its head; and they remain there, unhatched, 
although the embryo may be fully developed, until 
the horse in licking itself or a companion dislodges 
the egg-cap and, freeing the larva, transfers it to the 
mucous membrane of the mouth. From this place it 
moves at once and makes its way down the oesophagus 
into the stomach. Here the young bot finds its proper 
conditions and becomes anchored by means of a pair 
of mouth hooks into the lining membrane. It feeds 
here, absorbing the juices for several months, maturing 
in late spring, and then loosens its hold, is carried into 
the intestines with the excrement and so on through 



RELATION TO OTHER ANIMALS 



179 



the anus. When it reaches the ground it burrows into 
it at once, changes to a pupa, and not until a month 
thereafter does it transform into an adult fly. A full 
year is thus required for the development of the species, 
and there is only one danger season for infection — the 
period during July and August when the flies are on 
the wing. 




Fig. 80. — The horse bot, Gastrophilus equi: a. egg. attached to hair; b, young; 
c, full-grown larva; d, adult fly; c, hooks of larva. 



A few bots, while not of course an advantage, will 
not hurt a horse. More than a few will cause trouble, 
in proportion to the amount of infestation. There is, 
naturally, the irritation to the membrane to which the 
insects are attached, causing digestive derangement; 
there is also the positive drain upon the system by the 
feeding maggot which is apt to weaken the animal and 
to intensify the effect of the digestive trouble; and 
finally, when there are many bots, they tend to form a 
mechanical obstruction to the passage of food from 



i8o INSECTS 

the stomach to the intestine, A bad infestation is a 
serious matter and may easily become fatal. 

On well-cared-for horses bots are not often trouble- 
some. The eggs are readily seen and as they cannot 
be hatched for several days after being deposited, 
they may be easily removed when the animal is groomed. 
They are firmly enough attached, however, not to 
be easily removable by the horse, and the embryo 
develops within ten days after they are laid. If at any 
time after that the egg is licked, the cap covering the 
top opens and the larva slips out of the shell on to the 
tongue, moving actively at once toward the gullet. 
A thorough brushing and washing once every week 
will therefore be sufficient to keep a horse free, even 
when exposed to the attacks of the flies. 

It is curious to note how all animals subject to bots 
appear to dread the adult flies. They cannot possibly 
know the relationship between the flies and the bots, 
and it is probably the apparent intention to attack 
that arouses the fear that undoubtedly exists. 

Homed cattle are subject to the attacks of bots 
that form swellings or "warbles" under the skin, 
usually on each side of the backbone; and these insects 
affect not only the general health of the animal, but 
very materially reduce the value of its hide. In fact 
the impairment of value so caused has been reckoned 
at many millions annually while the impairment in 
value of dairy products, due to the poor condition of 
suffering cows, can hardly be estimated. 

The hfe cycle of this species is also interesting and, 
in a way, decidedly more compHcated than that of any 
of the species previously referred to. The adult is not 
so unlike that of the horse bot; a little more compactly 
built, with a shorter abdomen and a somewhat banded 
appearance in black and whitish. Like its ally it lays 



RELATION TO OTHER ANIMALS i8i 

its eggs on the hair of the animal it infests, and here 
also further development is dependent upon the in- 
troduction of the young larva into the mouth. But 
there the resemblance ceases, for the young larva, in- 
stead of permitting itself to be carried to the stomach, 
attaches itself to the walls of the oesophagus and bores 
its way through into the muscular tissue, continuing on 
until it reaches the desired position beneath the skin. 




-The ox bot, Hypoderma lineata: a. eggs attached to hair; 
b. fly; c, larva. 



As with the horse, the well-cared-for dairy animal 
rarely suffers from bots; the eggs are so conspicuous 
that they readily attract attention, and removal is 
easy. If any do escape and bot-swellings are noticed, 
they should be lanced and the contained larva removed. 
Cattle on the range or beef cattle in pasture suffer much 
more, because they are less or not at all looked after, 
and the bots are not suspected until the ulcerating 
sores attract attention. 

A still more highly specialized type is represented 
by the "louse flies," sometimes separated under the 



i82 INSECTS 

term Pupipara, or those that give birth to pupae. They 
are usually active, flattened, brown or yellow flies, 
with small head and rounded abdomen. Some of them, 
infesting birds of prey, fly actively, while others, like 
the "sheep tick," are wingless, although not there- 
fore inactive. They are called pupipara because the 
egg hatches within the body of the female and the 
larva attains its entire growth before being extruded, 
ready to pupate. Of course this means a very slow 
rate of reproduction, since the numVjer of young matured 




Fig. 82. — A louse fly, Olfcrsia species. 



at one time cannot be great; but, on the other hand, 
it is also a safe rate, because the larvae run few dangers 
during their early life, and the infant mortality is not 
very high. Nestlings become infested from the mother 
bird, and the flies are quite active enough to make 
short flights from the host and back again when neces- 
sary to escape an especially vigorous hunt. When 
the host dies or is killed the parasites leave it at once, 
and seek shelter on any living thing in the vicinity. 
"Sheep ticks" which, as already indicated, are 
wingless, do really look very much more like ticks 
than like flies; their long mouth parts, small thorax, 
long legs and round flattened abdomen giving them 



RELATION TO OTHER ANIMALS 183 

a peculiarly spider-like appearance. They are some- 
times very abundant on sheep, and find no difficulty 
in getting on to new animals because of the habit of 
congregating into dense masses, peculiar to their host. 
The body of these flies is very tough and leathery, and 
I am informed by those who handle the raw hides 
that they will survive all the preliminary handlings, 
cleaning and soakings which the pelts undergo before 
being denuded of wool and prepared for tanning. 
Herders know of a great variety of "dips" useful 




Fig. 83. — Sheep tick, Melophagus Fig. 84. — A bat tick, 

ovinus. Nycteribia. 

against these insects and "dipping" is a regular prac- 
tice wherever sheep are raised in any numbers. 

The extreme development in this direction we find 
in the bat ticks, which are even more spider-like than 
the sheep tick and have similar habits, while infesting 
a much-shorter-haired animal. It is distinctly curious 
that while there are many species of these louse flies 
among birds, there are only a few, very aberrant forms, 
that have adapted themselves to live on four-footed 
animals. 

We find, then, that among the insects there are foes 
to almost all kinds of vertebrates and that they are 
not at all despicable foes. While the death of the 
animal attacked is never sought as a prime object, 



i84 INSECTS 

it not infrequently follows as the result, and it is not 
by any means easy, even for man himself, to guard 
against injury in all cases. 

We see also that parasitism is not by any means a 
primitive condition but an adaptation, frequently 
accompanied by specialization of a high order. It is, 
in some of its manifestations, of comparatively recent 
origin, the greatest diversities obtaining in the highly 
specialized Diptera, while the simple forms are all 
in the more generalized orders, being there little more 
than an adaptation to life on an animal rather than 
on a plant. 



CHAPTER VIII 

THEIR RELATION TO MAN AS BENEFACTORS 

Insects as benefactors to the human race have 
been very Httle considered, their position on the op- 
posite side having been so much more emphasized ; 
and yet, if some few species were ehminated, their ab- 
sence would be very seriously felt for a time, until a 
substitute for them could be discovered. Possibly 
the reference to them as benefactors is a little inac- 
curate for most of those referred to here — they are 
useful to man rather than his benefactors. We might, 
of course, class as benefactors those that pollenize his 
fruits and. other crops; but there the benefit is indirect 
as to man, and more direct as to the plants, hence coming 
under another head. 

Directly beneficial to man are those insects that 
act as scavengers, working to reduce to their original 
inorganic compounds those animal and vegetable 
materials that are dead or dying and of no further use 
as living organisms. The extent of the benefit thus 
derived is absolutely unappreciated; but were all 
insect scavengers removed at one time and all dead 
animal and vegetable material left to other decays, 
the foulness and noxious odors that would be thus let 
loose are beyond all description. 

Does a small animal die in the field — within a few 
hours burying beetles are working to get it under- 
ground; flies have laid their eggs on the body and 
numerous other species have begun feeding on the skin, 
the hair and the flesh. Within twenty-four hours in 
summer, the process of disintegration is well under 
185 



i86 INSECTS 

way and in a remarkably short time nothing but the 
bony framework remains. 

Hardly has a cow dropped a mass of excrement 
in the pasture, before it is covered with flies absorbing 
the moisture, helping to form a dry outer coating and 
ovipositing for maggots to help reduce the half-decayed 
mass into fragments that may be mingled with or ab- 
sorbed by the soil. If, after a dropping has been in 
the field forty-eight hours, it is broken up in a pail of 
water, the number of specimens and species that will 
come to the surface is startling. 

Is a forest giant stricken and borne to the ground 
by wind, flood or lightning — immediately insects of 
many sorts attack and begin to reduce it to dust, con- 
tinuing their work until nothing remains. And so of 
all organic matter in which life is waning or from which 
it has departed — such matter is prey to insects and they 
are never backward in fulfilling their duty. 

This scavenger function is by no means a "low," 
or "primitive" habit; it does not exist in the lowest 
orders at all and is best developed in the Colcoptera 
and Diptera, which are among the highly specialized 
and dominant types. To be sure the Thysanura are 
largely feeders on the products of decay and hence 
may seem to be entitled to rank as scavengers; but 
they rather come after decay and feed on its products, 
hence their presence is merely indicative of moisture 
and decay produced by other causes. 

The Termites among the Neuropterous orders are 
feeders on wood and other vegetable products, but they 
invade rather for building purposes and are never 
found in really decaying material. 

The order Hemiptera contains no scavengers among 
either the Homopiera or Heteroptcra and stands entirely 
free from even a tendencv in that direction. 



THEIR RELATION TO MAN 187 

In the Coleoptera or beetles there are several families 
that are scavengers in whole or in part, and some of 
these families contain very large numbers of species. 
In a very general way the scavengers may be recog- 
.nized bv the clavate or club-shaped antenna, combined 
with five-jointed feet or tarsi, and thus belonging to 
the series " Claviconiia." 

The StaphyiinidcB or rove-beetles are found wherever 
decaying or fermenting material occurs, although by 
no means all the Staphylinids are scavengers. They 
are long, slender, somewhat flattened beetles, with 
wing-covers or elytra extending over only two segments 
of the abdomen. The other segments are free and 
flexible, often readily up-curved so that it sometimes 
appears as if they intended to sting. Some of these 
species are so small and slender that they are difficult 
to see and some are of considerable size; sometimes 
they are smooth and shining and sometimes densely 
covered with short silky pile, both methods serving 
to keep the insects clean in their often unsavory sur- 
roundings. As an indication of their habits some of the 
species have peculiarly sickening odors that in penetra- 
tion and volume are altogether out of proportion to the 
size of the insect producing them. In animal or vegeta- 
ble decay, in excrement, under and in dead animals, in 
the fermenting sap of injured or dying trees, in fungi of 
all kinds — in all these places our Staphylinids occur and 
everywhere do their share of the needed work. 

Closely allied to them come several families of 
minute beetles, some of them of odd and bizarre shapes; 
all of them with the enlargement or club of the antenna 
well marked, and all of them feeders on dead or decay- 
ing matter. Their names alone would tell us nothing; 
to go into their habits and peculiarities would require 
another book, for there are literallv hundreds of them. 




i88 INSECTS 

Conspicuous in appearance and habit are the bury- 
ing beetles and carrion beetles, their names indicative 
of their functions. They are often of moderate or large 
size and at the end of the feelers the club is capitate or 
shaped like a head, an arrangement that permits the 
organization of an extremely sensitive olfactory system. 
The sense of smell in these insects is so well developed 
indeed, that even a small dead animal is unerringly 
located very soon after its 
demise. I have seen these 
beetles climb to the tip of 
a twig, extend the antennae 
in every direction with the 
leaves of the tip widely sep- 
/ '"^^ arated, and then fly in a 

straight line and without hes- 
N itation in the direction from 
I ^, , which, apparently, an agree- 

^^J^H^** I able odor was perceived. The 

^^B^ yS burying beetles are so called 

^ \ because of their habit of 

•^ digging out the soil from 

^'"'Vwrat^.t:!';;^"^^^' beneath a small animal un- 
til it sinks down to or below 
the level of the ground, and the powerful head, thorax 
and legs are well adapted for this kind of work. The 
carrion beetles are quite as prompt in their arrival, 
but do not work in the same way. They are content 
with ovipositing on or under the cadaver, trusting the 
resulting larvae to their own devices. And what a lot 
and variety of these carrion beetles there are! Species 
so small as to be almost invisible to the unaided eye, 
and others an inch or more in length. Species smooth 
and shining so that none of the material in which they 
live can adhere to them, and species covered with fine 



THEIR RELATION TO MAN 189 

silky pubescence, or rough and ridged for the lodgment 
of any sort of material, serving in some cases to disguise 
and conceal. And as with most of the scavenger fam- 
ilies, not all of the species are confined to animal foods. 
Some are found in decaying vegetation, and yet more 
in fungi, which harbor a great number of species. 

The HisteridcB or "pill beetles" are little, chunky 
creatures shining black or metallic in appearance, and 
the legs all broad and flattened, fitted for digging. 
They occur in decays and ferments of all kinds, but 
their habits are more diverse than in some of the other 
groups, predatory forms being not uncommon. 

And then come those species allied to the Dcnncs- 
tidcc or larder beetles; species that feed upon dead 
organic material but which instead of being advan- 
tageous are rather the reverse, since they often feed 
upon material that man desires for his own use, like 
dried and smoked meats, hides and even the animal 
fabrics. Here again we note that the matter of use- 
fulness is after all only a relative one, since the very 
function that makes a species valuable when it affects 
something of no use to man, makes it harmful when it 
affects something that he wishes to keep. 

There are exceptional scavengers in most of the 
other beetle families, but none that need mention 
here except the "tumble-bugs" and their allies, which 
feed on excrementitious material, often rolling large 
balls of dung from the place where it was found to a 
place w^here it can be conveniently buried to serve as 
food for their larva?. These tumble-bugs are members 
of the Lamellicorn series which contains mostly plant 
feeders and which are more fully referred to as plant 
enemies. 

The Lepidoptcva contain no scavengers strictly 
speaking, although there are some species that feed 



igo 



INSECTS 



on dried organic matter, animal as well as vegetable, 
and in the Hymenoptera only the ants may be classed 
as such. Ants, of course, are feeders on a very great 
variety of materials. Some species will attack and 
devour any living thing that comes in their way ; others 




■A " tumble- buR, " Copris Carolina: a. larva; b, the cell in which 
it lived; c, pupa; d, female beetle. 



confine themselves to vegetable food only and yet 
others seem to be restricted to liquid food. Most of 
them have quite a range of supplies and some species 
may be found almost anywhere, even in our houses. 
And yet ants are rarely thought of as real scavengers, 
for they are not seen in or on decaying animals or in 
or on foul excrements. 

In the Diptera, however, we have scavengers in 
great number and variety; and yet very much ahke 



THEIR RELATION TO MAN 



191 



after all, for in the larval stage they are nearly all mag- 
gots, similar to those of the common house fly. Wher- 
ever an animal dies, a mass of excrement drops in the 
field, an over-ripe fruit falls to the ground or a pail of 
garbage is set outdoors, there we find flies present at 
once and in a few hours young maggots. It has been 
said that flies will devour an ox more rapidly than a lion 
and while that may be a little exaggerated, they will 
certainly make a more complete job of it. It is literally 




Fig. 87.' 



-Pommace fly; Drosophila ampelophila: a, adult; b, larva; 
d, e, pupa. 



astounding to note how rapidly a small carcass may be 
transformed into a mass of squirming maggots, ap- 
parently liquefying the tissues so that they may be ab- 
sorbed through the small mouth orifice. And it needs 
so little to attract these flies. Lay out a few bruised 
apples, pears or other fruit on a table, and in a short 
time they will be covered with little yellowish or gray 
flies having bright, brick-red eyes — pommace flies — 
coming from no one knows where, but attracted by the 
odor of the ferment. In the fall when cider or wine is 
making, every tub or barrel of must is an attraction, 
and in the ferment thrown out of the bung of the wine 
cask the larvae occur by the hundred. Not long as 



192 INSECTS 

larvae either, for in two or three days they have become 
full-grown, change to a pupa and then to the adult 
condition. And so we find that in this, the most highly 
organized series of insects, scavengers are numerous and 
effective. So effective, indeed, that their usefulness is 
not recognized by the average man, because he has no 
chance of knowing what conditions would otherwise be. 

Among the insects of direct use to man none are of 
greater importance than the silk-worms. Silk is in 
such general, almost universal, use, that there is scarcely 
a moderately well-dressed individual of either sex 
that does not have some of it as part of a garment 
or other article of wear. Of the millions who wear or 
use silk how many ever know, or knowing, realize, that 
every particle of that silk is the product of a cater- 
pillar; nothing more than a dried viscid salivary secre- 
tion, originally intended by nature as a covering to 
protect the pupal stage of the insect? This covering 
or case is called a cocoon, and cocoons are spun by 
many caterpillars, some of them much larger than the 
Chinese silk- worm. 

Why, then, if there are many silk spinners do we 
use one only, and what particular advantage has the silk 
of this species over all others? As to the latter, it has 
few advantages over other caterpillar silks: it is not 
nearlv so strong as some produced by other varieties, 
it is not more lustrous, and it is not nearly so great in 
quantity. Its one great advantage for our use is that 
it can be more easily reeled than any other known 
variety. The silk- worm, when ready to make its cocoon, 
spins a small quantity of loose supporting threads or 
floss and then starts inside this framework, spinning 
with a continuous thread, unless interrupted, until 
the entire cocoon is completed — a thread almost a mile 
long which, under favorable conditions, can be unwound 



THEIR RELATION TO MAN 



93 



in the same way and without a break! Generally, 
other caterpillars that spin cocoons do not work con- 
tinuously; or if they do work steadily on, they make 
a patchwork affair of it. They may spin a few yards 
at one end, break the thread, put in a few yards at an- 




Silk-worm. cocoon and male moth. 



other point, and so on until the work is completed, 
making a nice even job when everything is done, but 
a cocoon that cannot be profitably unwound or reeled 
because of the great number of breaks. 

Then, too, the particular species, Sericaria mori, 

has been domesticated so long that it has developed 

some highly desirable qualities. The adult moths are 

very sluggish, even the males flying little or not at all, 

13 



194 



INSECTS 



while the females are practically incapable of flight. 
They pair readily in confinement, are hardy, and very 
fecund, the female producing several hundred eggs. 
All these advantages, together with the ease of handling 
the caterpillars, are matters in favor of the mori, and 
its propagation is largely the work of women and 
children who do it as a side issue and hence very cheap- 
ly. It is this latter factor indeed that has barred silk 
culture in America, where the cost of labor is too high 
to make the venture attractive to any class. 

It has already been said that the silk is in the nature 
of a salivary secretion; but that is only partly true, 




Secret mg C/dnds 



Fig. 89.— Salivary gland of silk-worm. 



because, although the material is secreted by one pair 
of what are usually salivary glands, these glands have 
been so enormously enlarged that they extend along 
the sides of the body for almost the full length of the 
caterpillar, and the material has become so sticky and 
viscid that it could not possibly have any digestive 
function. The two glands unite into a single outlet 
on the lower lip of the caterpillar, and as soon as the 
fine thread of liquid issues from the opening of the 
spinning organ and comes into contact with the air, 
it hardens sufficiently to hold its form, reaching its 
full strength and elasticity a few moments later. As 
to the value of silk products each year, they must be 
figured in millions of dollars, so that the humble cater- 



THEIR RELATION TO MAN 195 

pillar adds not a little to the wealth of the producing 
countries, and to the support of those engaged in textile 
industries. The elimination of the silk-worm and its 
product, while it would not eventually cause mankind any 
serious inconvenience, would deprive it, for all time, of 
one of its most valued and widely employed fabrics. 

Next in order of value are the bees and bee-products 
which seem to have been recognized and employed 
almost or quite as long as we have any historic records. 
Honey from wild bees is known to every savage nation 
and has formed an important item of food. And not 
of food alone, for away back in the dark ages it was 
found that it made an excellent drink when fermented, 
the "meth" of the ancient Saxons being the ancestor 
of the "metheglin" of more recent times. The latter 
drink is little known now-a-days, especially in cities and 
towns where malted and distilled liquors are in use; 
but it has still a vogue in a few sections of the country, 
where those who first make its acquaintance gain a 
wholesome respect for those ancestors of ours wliose 
capacity for it was measured by "flagons," or "horns." 

Wax and honey as products of the bee are uni- 
versally known and the organization of the beehive is so 
well understood that it need only be referred to. Paraf- 
fine has largely supplanted beeswax for many purposes, 
while sugar and glucose have replaced honey; so, even 
were the bee now completely eliminated from our fauna, 
mankind would still worry along. Nevertheless, bee- 
products are on the increase rather than otherwise and 
there is no lessening in the demand for them. 

The products of the "lac" insects known as "stick 
lac," "shell-lac," etc., are yet of considerable impor- 
tance although the insect "lac" has now been largely 
replaced by cheaper preparations from other sources, 
for general use. The lac insect is really one of the "soft 



196 INSECTS 

scales," allied to the most serious of our tree pests: 
indeed it is a tree pest, tolerated only because the insect 
is of more value to us than the plant upon which it 
feeds. Infested twigs are cut and stored when the insect 
has reached the proper stage, and the adherent scales 
and their secretions are dissolved off when they are to be 
commercially used. Lac is a product of the Orient and 
many of the fine polishes and lacquers of Indian, Chinese 
and Japanese workmen are based upon it. There are 
allied species of Coccidce occurring in tropical America; 
but none that have been made commercially useful. 

Cochineal as a source of a beautiful crimson and 
scarlet is well known and is also a scale insect or Coccus, 
belonging to the mealy-bug series. It infests certain 
kinds of cacti and is cultivated in plantations called 
"nopalries. " It is the source of the coloring matter 
known as crimson lake, and is a native of Mexico and 
Central America. Before the day of aniline colors 
cochineal was extremely valuable and important; but 
at present the complete elimination of the insect would 
cause little if any inconvenience. 

It is noticeable that, except in the case of silk, we 
have substitutes for practically all the insect products 
and even silk has been artificially produced, i.e., a 
product so closely resembling it as to be called artificial 
silk has been made that could be developed practically 
in case of necessity. 

In olden days insects had a wider use, and out of 
a plague a food supply was sometimes developed. 
"Locusts" or grasshoppers as articles of food are known 
among barbarous nations of many countries where 
the insects are sufficiently abundant. The Indians of 
the Rocky Mountain regions in America and the 
aborigines of Africa were equally familiar with a grass- 
hopper diet and with the methods of preparing them. 



THEIR RELATION TO MAN 197 

It has even been suggested that there is no reason why 
they should not be retamed on our modern bills of fare, 
and experiments have been made in different methods 
of preparation. Fried they are said to have a sweet, 
nutty flavor, while in a stew with milk they recall 
oysters. It must be confessed that no very great en- 
thusiasm has ever been developed for this kind of diet, 
and on the whole the use of grasshoppers for food pur- 
poses is distinctly on the wane. 

In South America a species of water bug of the Corixa 
series occurs in great abundance in some localities and 
lays its eggs in large numbers on the surface among the 
sedges. These eggs are gathered, dried and preserved by 
the natives, who mash and bake them into a cake that 
is much appreciated. Inasmuch as the eggs have a very 
decided bed-buggy odor, it would require considerable 
education to make that sort of omelet popular. 

The large boring larvte of Coleoptera and even some 
Lepidoptera are not unusual articles of food in tropical 
countries, and ants or ant larvae and pupae have also 
served as sources of food supply to uncivilized man; 
but as civilization tends to eliminate the insects in its 
advance, their decreased numbers w^ould render them 
less available as sources of supply even were better or 
more usual articles not more plentiful. 

Galls as sources of supply for tannic acid are still 
gathered in some localities, and some forests are com- 
mercially profitable as gall producers. When inks were 
largely dependent upon galls for their black color, there 
was a greater demand for them than now, when chem- 
istry supplies other if not better sources of more or less 
permanent black stains. 

Insects have from time to time served as ingredients 
in medicaments ; but very few are so used at the present 
time. Of these the Cantharides or blister beetles are 



198 INSECTS 

best known and yet most widely employed. In the 
body juices there is secreted an extremely irritating 
material known as cantharidin which, when applied 
to the skin, produces blisters or, taken internally, pro- 
duces inflammatory conditions of the genito-urinary 
system. Most of the blister beetles possess this prop- 
erty to some extent, and a fresh specimen of any of 
the common American species crushed upon the skin 
will produce blisters; but the ofhcinal preparations 
are obtained from a European species, known as the 




Fig. yo. — Spanish flies, Lytta vcsicatoria. 



Spanish fly, Lytta vesicatoria, from the locality whence 
most of the specimens come and from its vesicating 
properties. These beetles come in great swarms when 
they emerge and are on the wing for a few days only, 
during which period the entire country is engaged in 
gathering them in sheets on which they are killed and 
dried, after which they may be preserved indefinitely. 
The blistering property is dissolved out of the powdered 
beetles with alcohol. 

Broadly stated there are no insects that are indis- 
pensable to man; there are a few that are very use- 
ful to him, aside from those that arc plant pollinators, 
and he makes use of a few others for which he has 
substitute materials at hand and already in partial use. 



CHAPTER IX 

THEIR RELATION TO MAN: AS CARRIERS 
OF DISEASES 

Since the development and general acceptance of 
the microbian or "germ" theory as applied to many 
contagious and infectious diseases, and its absolute 
demonstration in plagues like cholera, typhoid fever, 
dysentery and other enteric or intestinal troubles, as 
well as in consumption, pneumonia, diphtheria and other 
afifections of the respiratory organs, the question of the 
agencies concerned in the distribution of these germs 
has come to the front. 

The surgeon has long known that suppurations and 
pus-producing inflammations might be carried from one 
individual to another by almost any sort of carrier; so 
when he operates, he sterilizes his instruments, his 
hands, the cut or bruised surfaces, and protects the 
wounds by antiseptic dressings. That flies were among 
the agencies for spreading suppurations was soon 
learned, and the readiness with which flies gather on 
sores or raw surfaces is matter of common observation. 
When it was observed that flies of various kinds gathered 
with as much readiness on fecal or excrementitious 
matters as on food products in the kitchen, and were 
ready to change their diet from one to the other without 
much provocation, the conclusion that they might inocu- 
late the food products and through them healthy indi- 
viduals from the fecal matter was not a difficult one 
to draw. 

In the cholera epidemic at Hamburg not so many 
years ago, this was absolutely demonstrated as to that 
199 



200 INSECTS 

disease. It remained for the United States, during its 
war with Spain, to demonstrate with equal positiveness 
that typhoid and other enteric fevers could be carried 
in the same way. More soldiers killed by common 
house flies than by Spanish bullets, is the unenviable 
record, and the most unsafe places for our soldiers were 
the fly-infested home camps where open latrines and 
near-by mess tents furnished ideal conditions — for the 
flies and the diseases. 




Fig. 91 



-The house fly, Musca domestical larva with details at right, puparium 
at left. 



While flies are not the only carriers of enteric disease 
germs and these do not actually depend upon insects as 
their sole means of spread, yet the habits and structures 
of flies are peculiarly adapted for effective service of this 
nature and they are correspondingly dangerous. No 
other insects live in such close communion with man, and 
so much are they regarded as a matter of course that 
their companionship at our table arouses no fear; and 
such is their persistence that they gain admittance to 
the palace of royalty, as well as the hovel of the peasant. 
They breed in all sorts of decaying and excrementitious 
matter, in garbage pails and even in neglected corners of 



THEIR RELATION TO MAN 201 

cellar or store-room; a very little material serving to 
mature a large number of speciinens. The common 
house fly, Musca domestica, prefers horse-manure for its 
development and is most numerous in the vicinity of 
stables. The eggs are laid in little masses by the adults, 




Fig. 92. — Foot of the house fly: a, the last tarsal joint and claws; b. claws and 
pulvilli; c, a small section of the pulvillus, showing hooked hairs. 



the larvae or maggots hatch almost at once, and a week 
later these are full grown and ready to transform. 

On the soles of their feet flies have pads of very fine 
hair, which serve excellently as gatherers of micro- 
organisms from the surfaces over which they travel, and 
equally well as distributors on others over which they 
may track later. This point has been proved experi- 
mentally by allowing flies to walk over cholera excre- 



202 INSECTS 

tions, and afterward over plates of prepared gelatin. 
In the incubator, every footprint developed a flourish- 
ing colony of virulent cholera germs. 

The mouth parts of flies are almost equally well 
adapted for similar purposes. At the end of the fleshy 
lips are lobe-like expansions furnished with chitinous 
ridges by means of which the pasty masses of food are 
scraped into shape to be ingested by the insect. These 




Fig. 93. — Lapping organ at the tip of the fly mouth. 

ridges are excellent resting places for the minute organ- 
isms and, when the flies change their diet, the germs are 
directly inoculated into the new food material, what- 
ever its character. And flies are not always cleanly in 
their habits, but void their excrement anywhere in 
small, pasty masses which dry quickly. It has been 
shown that the bacilli of intestinal troubles pass through 
the digestive tract of the insect unchanged, hence every 
"fly speck" may be a source of danger. 

This method of transfer for pathogenic organisms is 
very simple and direct, and is applicable only to forms 




THEIR RELATION TO MAN 203 

that undergo no change and which, when implanted in 
a suitable medium, will continue their growth and 
increase with unabated virulence. We have yet quite a 
different class of diseases, also due to microscopic or- 
ganisms, but of an altogether different type: minute, 
single celled animals in fact, that live in special body- or 
blood-cells, but are not capable of completing their en- 
tire life cycle in a single host. 

The best known example of this sort of infestation is 
that due to the Plasmodium parasite which produces 
what is loosely known as malaria. It is not so long ago 
that almost any sort of indefinite 
illness was likely to be classed as a 
"touch of malaria:" now-a-days 
when a doctor diagnoses "mal- 
aria" he refers to an affection 

Fig. 94. — Part of one 
caused by one of two or three of the pseudo-trachea used 

specific organisms that have very -« ^^^--^P'^g °^g^"- 
definite life cycles and produce 

very definite results. All of them agree in being Spor- 
ozoa, i.e., animals that reproduce by means of spores, and 
in that they do not complete their entire life cycle with- 
in the body of their human host. The parasite producing 
the ordinary type of tertian malaria or " chills and fever " 
lives in the red blood-corpuscles of the human body and 
comes to maturity in such a blood-cell in forty-eight 
hours. It then breaks up into a mass of minute spores 
which rupture the cell and are liberated into the blood- 
scrtmi. In this they float about for a short time, and 
then each spore makes its way into a sound red blood- 
corpuscle, and in forty-eight hours is itself mature and 
in turn reproduces in the same way. As all the parasites 
come to maturity and liberate their spores at about the 
same time, this causes a disturbance of the body tem- 
perature resulting in a chill, followed by a fever when the 



204 INSECTS 

spores are entering new blood-corpuscles. In other words 
the "chills" and "fever" merely emphasize the period 
at which the parasite sporulates, and the ill effects of 
malaria are due to the gradual destruction of the red 
blood-cells. 

If some of this infested blood be drawn from a pa- 
tient and injected into the circulation of a healthy indi- 
vidual, a new case of malaria will result; but in no other 
way can there be a direct infection from one individual 
to another. Normally this reproduction by means of 
spores continues in an infested individual for some time 
and then, in addition to the spores, special cells develop 
which, when liberated into the blood-serum, make no 
attempt to enter new blood-corpuscles. These are the 
"gametes," of two types, differing a little in size and 
form and termed respectively "micro-" and "macro- 
gametes. " They undergo no change in the human body 
and may remain in that stage for an indefinite period, 
even when the active reproduction of the Plasmodia 
has been checked and the patient is apparently well. 
Taken from the human body by any sort of blood- 
sucker or even drawn on a properly prepared slide, 
further development takes place. From the micro- 
gametes slender, whip-like processes are produced, 
known as "flagellae," and these break off and represent 
the male element that unites or conjugates with the 
large unaltered " macrogamete " representing the female 
element. At this point development stops unless the 
blood is in the stomach of a mosquito belonging to the 
genus Anopheles. If it is not only Anopheles, but a 
member of the right species, the conjugated gamete 
elongates and becomes a "vermicule" which bores into 
the tissue of the mosquito stomach, increases in size and 
gradually works its way to the outer surface where it 
forms a little lump or protuberance, now known as a 



THEIR RELATION TO MAN 



205 



"zygote." In about ten days this form matures and 
bursts, liberating thousands of "blasts" or " sporo- 
zoits" into the body cavity of the mosquito. In 




Fig. gs. — Anopheles and Malaria; o, larva; b, pupa; c, adult; d, the blast 
introduced into the blood by the mosquito; e to ;', stages through which the 
Plasmodium passes in the red blood-corpuscle; k, the spores which enter new 
blood-corpuscles; /, m, the microgamete; n, o, the macrogamete; p, flagella; 
forming; q, union of a flagellum with macrogamete; r, fusion of nuclei; s. the 
vermicule; t to y, formation of the zygote in the mosquito stomach; the fully 
developed zygote, y, rupturing to produce blasts d. 



2o6 INSECTS 

some way these gather into the saUvary glands, and 
when that mosquito bites again, it introduces with its 
droplet of saliva a large number of "sporozoits" which, 
if they find conditions favorable, enter red blood- 
corpuscles and set up a case of malaria. 

The transmission of this disease, then, is by no means 
a simple matter, and the proper species of Anopheles is 
absolutely essential to it. The elimination of these mos- 
quitoes from any locality would carry with it the elimi- 
nation of malarial troubles as well. It may be inter- 
esting to note in this connection that the species of 
Anopheles live easily in settled communities, enter 
houses freel}' where they can manage it, and that the 
female passes the winter in the adult stage in cellars, 
coming up occasionally into well-warmed rooms and 
even biting. Normally, they do not become active 
until well along in May or in June, when eggs are 
laid by the female which has been fertilized the 
previous fall. 

All stages of the parasites causing the various forms 
of malaria have been followed in both man and the 
mosquito, and no part of the history above given is 
guess-work. The connection between the Stegomyia 
mosquito and yellow-fever is equally certain, though the 
specific parasite has never been made out in either man 
or insect. Direct experiment has furnished convincing 
proof of the connection, and the treatment of yellow- 
fever epidemics has entered a new phase. The efficient 
work done in the Panama Canal Zone has demonstrated 
that the disease is quite controllable through the insect 
and, incidentally, collections made by entomologists 
from the U. S. Department of Agriculture at Washing- 
ton, have shown that this Stegomyia is never found 
away from human settlements. The relation, then, is 
extremely close between this insect and man, and they 



THEIR RELATION TO MAN 



207 



are both needful to the continued existence of the 
disease. 

There are other tropical fevers that are probably as 
much dependent upon other mosquitoes, but we know- 
less about them. We do know that several forms of 
bird malaria, due to species of Proteosoma, are also de- 
pendent upon mosquitoes as intermediate hosts, and 




Fig. 96. — The Tsetse-fly, Glossina morsitans. 

how many diseases of other animals are transmitted by 
them is as yet matter of conjecture only. 

A species of Culex very closely allied to our common 
"house" or "rain-barrel" pest is responsible for the 
transmission of that tropical disease "filariasis" which 
sometimes causes the abnormal enlargement of the 
lymphatics and thickening of the skin, known as "ele- 
phantiasis." Other species have been charged with 
being agents in the transmission of leprosy, but this 
must be considered "not proven" as yet. 

In all these cases, the mosquito is an intermediate 
host: not a mere carrier, but a fellow sufferer with 
man, subject to another form of the same disease. 



208 



INSECTS 



and in this respect there is a fundamental difference 
from those troubles conveyed by house flies, which 
suffer nothing, and are purely mechanical transporters 
of the infection — albeit peculiarly well adapted for 
their purpose. 

There are other flies, however, that seem to be nearer 
the mosquitoes in this respect and, among these, are the 
species of Glossina or "tsetse" flies of South Africa, 
which are known to pro- 
duce fatal affections in 
horses and have been re- 
cently charged with being 
agents in the transmission 
of the " sleeping sickness. " 
All mosquitoes pass 
their early or larval stages 
in water, and that is about 
the only feature that is 
common to all of them. 
They differ widely in the 
character of the waters 
which they inhabit, in the 
period of development, and 
in the number of broods. 
Some pass the winter in the egg state, some as larvae 
and a very fair proportion as adults. All the species 
that are closely associated with man may breed in 
dirty water, and some in such as is absolutely filthy. 
Culex pipiens, the common "house mosquito," 
breeds in rain barrels, lot puddles, cess-pools, gutters 
and sewer basins. It is rarely found in clean water and 
almost never in streams or brooks. The eggs are laid 
in a mass or raft on the surface and are easily seen when 
their character has once been recognized. In forty- 
eight hours the larva is ready to hatch, a little lid drops 




-Larva and pupa 
mosquito. 



THEIR RELATION TO MAN 



209 



from that surface of the egg that rests upon the water, 
and the minute wriggler sHdes at once into its natural 
element. This "wriggler" is so named from its peculiar 
jerky mode of progression. It has, attached to its 
mouth, a pair of very dense brushes of fine hair, and 
these brushes are kept in constant motion, combing 
from the water and into the mouth the minute organisms 
upon which the creature subsists. At the other end of 
the body is a cylindrical tube of moderate length, at the 
tip of which are the spiracles or openings to the breath- 
ing tubes, by means of which air is secured from above 
the surface of the water; for the larva although strictly 
aquatic as to food and other habits, is yet dependent 
for its supply of oxygen upon the outer air, and must 
come to the surface at short intervals to breathe. Indeed 
the favorite position of this larva is to hang head down 
in the water, the tip of the tube at the surface, the 
mouth brushes hard at work securing food. This pecu- 
liarity of the insect gives us a certain advantage in our 
efforts to control their increase, for a film of oil on the 
surface of the water in which they live will prove rapidly 
fatal, the oil entering into the body through the spiracle 
when the insect attempts to get air. 

In from five to seven days during the summer, the 
larvae are full grown and change to pupae in which the 
outline of the future mosquito can be made out hunched 
into a comma-shaped mass. This pupa also gets its air 
supply from above the surface, through two small, 
trumpet-shaped tubes on the thorax, so that it is also 
fatally affected by oil. It is active in this stage when 
disturbed, and moves about rapidly but erratically, by 
means of two paddle-like structures at the end of the 
abdomen. When it becomes quiet it rises automatically 
to the surface, and there rests until ready to assume the 
adult stage, which is in from one to three days in summer. 
14 



210 INSECTS 

In cool or cold weather all the stages are lengthened and, 
whereas eight days from egg to adult is perhaps a normal 
period, this may be increased to two or even three weeks. 
The adult male is incapable of sucking blood; but the 
female is ready to bite twenty-four hours after she be- 
comes developed, and in three or four days thereafter is 
ready to lay eggs. The life period of the male is always 
short, since his only function is to fertilize the female. 
The life of the female depends upon her ability to find a 
place for her eggs. When she has placed them her pur- 
pose in life is filled and she also dies. If she finds no 
suitable place she may live for weeks and bite several 
times. Those females that develop late in fall do not 
feed after they are fertilized, but seek some convenient 
hiding place in a cellar, barn or outbuilding and remain 
there dormant throughout the winter. They become 
active again in May, but larvae are rarely found in any 
number until well along in June. This species occurs 
throughout North America and a close ally occurs in the 
old world. 

The yellow-fever mosquito, Stegomyia calopus, or 
fasciata as it used to be called, is a smaller species, black 
in color, with white marking on the body and legs. It is 
rather a pretty creature, an inhabitant of the more 
southern states and of the tropical and subtropical 
regions of America generally. On the Atlantic coast it 
does not extend normally north of Virginia, and this 
marks the limit to which yellow-fever may extend under 
ordinary conditions. I am not unmindful of the fact 
that yellow-fever has occurred in New York and Phila- 
delphia; but the conditions permitting these epidemics 
are now understood and cannot be again reproduced. 

In habit, the Stegomyia is not unlike C. pipiens, and 
like it breeds in all sorts of dirty water. It is very sensi- 
tive to cold, and the first frost puts an end to its activi- 



THEIR RELATION TO MAN 211 

ties. It is even more domestic than its ally and seems 
to be confined to the vicinity of human settlements. It 
is as susceptible to oil, in the larval stage, as any other 
species and also hibernates as an adult. The eggs are 
not laid in rafts, however, but are placed singly, not 
even necessarily in water, and may remain dry for a 
considerable period without losing vitality. When they 
do become water-covered they hatch, and the life period 
and stages are similar to those of pipiens. 




Fig. 98. — The yellow-fever mosquito, Siegomyia calopus: larva, pupa, adult. 



The species of Anopheles are longer and more slender 
than the Citlex, and the wings are usually more or less 
mottled or "dappled." The adult females hibernate in 
houses when they can get in, and in May or June lay 
eggs on the surface of water, singly or in little groups, 
but not in boats or rafts. They are kept afloat by a 
peculiar lateral supporting structure and hatch in a day 
or two after they are laid. The resulting larva or wriggler 
is altogether unlike that of Cidex or Stegomyia. It is 
flatter, with a proportionately smaller head and a much 
shorter breathing tube, and lies flat on the surface of the 
water. It has similar mouth brushes but gets its food 



212 INSECTS 

from organisms that float on the surface fihn. Its float- 
ing habit enables it to hve in very shallow water, and in 
places where no fish except the smallest top minnows can 
follow. 

For breeding places the species of Anopheles select 
moderately clean water, and prefer the grassy edges of 
large pools, ponds or swamp areas, or the eddies or dead 
comers of sluggish streams or ditches. They do breed in 
lot pools, however, and even in rain barrels, pails or tin 
pans. Cess-pools, sewage water or dirty gutters are not 
attractive to them. 

Despite this difference in habit the larvae are as much 
susceptible to oils as are those of Culex, and in the pupal 
stage the differences are much less pronounced. While 
in a general way, the species of Anopheles are referred 
to as malaria carriers, not all of them are able to serve 
as intermediate hosts. The most common and widely 
distributed form known to be dangerous is A. maculi- 
pennis, which has two fairly well-marked dusky spots 
on each wing. 

None of the domestic or house mosquitoes are great 
travellers, and they rarely fly for any considerable dis- 
tance ; but there are species breeding in the salt marshes 
along our coasts, both Pacific and Atlantic, that migrate 
long distances inland, drifting with the wind twenty 
miles or more in a single night. These species lay their 
eggs in the marsh mud and winter in that condition. 
The larvae, which resemble those of the house mosquito, 
develop equally well in salt or fresh water, and mature 
in about ten days from the date of hatching. In the egg 
stage they may remain dormant for months and perhaps 
for years. 

There are many other kinds of mosquitoes important 
as nuisances, but not a menace to health, whose consider- 
ation here would carry us beyond the scope of this essav. 



THEIR RELATION TO MAN 213 

The one uniform requirement for development — water in 
which they may breed — gives us the clew to the method 
of control, and our efforts should be intelligently directed 
to eliminating such places by draining or filling rather 
than to destroying the larvae after they have begun to 
develop. 

Sometimes, where it is recognized that mosquitoes 
are hibernating in numbers in a house or cellar, it may 
become desirable to attempt their destruction during 
the winter. This can be accomplished by fumigation 
with either stramonium or culicide. Stramonium is 
simply the powdered leaves of "jimpson weed," which 
grows almost everywhere within the United States, and 
it is made up with one-third its weight of saltpetre to 
make it bum better. Eight ounces of good stramonium 
is sufficient for 1000 cubic feet of space and the fumes 
are not poisonous to man. Culicide is a combination of 
equal parts by weight of carbolic acid crystals and gum 
camphor. Dissolve the carbolic acid crystals over a 
moderate heat and pour over the camphor broken into 
small lumps; the acid dissolves the camphor and the 
solution is permanent when kept in a stoppered jar. It 
requires three ounces of this culicide for every 1000 
cubic feet of space and it should be evaporated in a 
shallow pan over an alcohol or other lamp. This will 
kill flies as well as mosquitoes and is not dangerous to 
human life. The mixture is inflammable, however, and 
must be used with that fact in mind. 

Whichever of these materials is used, the room to be 
fumigated must be made as nearly air-tight as possible, 
and must be kept closed at least an hour to make certain 
of a satisfactory effect on the insects. 

Fleas are specialized flies, adapted for a particular 
mode of life, and their habit of more or less indis- 
criminate biting has laid them open to suspicion in 



214 



INSECTS 




F^G. 99. — A home-made evaporating outfit for "cul 
stovepipe. 



using a section of 



various directions. Their connection with the spread of 
the "plague" seems to be demonstrated and that disease 
is now fought in the rats from which the fleas transmit 
it to man. 



THEIR RELATION TO MAN 



215 



Fleas live in their adult stage on hairy, warm- 
blooded animals, feeding on their blood, and their trans- 
versely flattened form set with spines all directed back- 
ward enables them to move about freely and quickly. 
Their eggs are dropped in the dens or nests of their 
hosts, and the larvae, which are slender, white and 



i_>-4 




-The common cat and dog flea: a. the egg; b, adult; 
d, larv'a coiled in silken case; e, lar^a. 



worm-like, live on the dead and decaying animal and 
vegetable matter always present in such places. In 
houses, the common dog and cat flea is able to develop 
its larvae in the material accumulating in the crevices 
between floor boards and similar situations, and in the 
adult stage almost any kind of flea will bite any warm- 
blooded animal upon which it may happen to get, even 
if not capable of maintaining itself there. So man, 
though unfitted because of his hairless skin to serve as 



2i6 INSECTS 

a host for fleas, may nevertheless be bitten by any of 
those infesting any of the animals that live with him 
or in his dwelling places. 

In an ordinarily well-kept house flea larvae cannot 
develop; but occasionally, when such a house has been 
kept shut up during a summer, a brood of larvae may 
develop and become annoying. In such case a free use 
of gasoline in floor cracks and similar places where the 
flea larvae live will generally give relief. 

The subject as presented here is a mere outline of 
what is known and believed; there are other insects 
that undoubtedly facilitate the spread of disease in man, 
directly or indirectly, and there are many more that do 
this for other vertebrate animals. Their importance 
from this point of view cannot be overestimated, and at 
the same time it is eloquent testimony that for many 
ages man and these insects must have dwelt together, to 
permit so close a union as identity in parasitic affections 
argues. 



CHAPTER X 

THEIR RELATION TO THE HOUSEHOLD 

Since man has enjoyed the shelter of a dvvelhng, how- 
ever simple, he has had in it something in the nature of 
furniture and bedding, and he has usually felt the need of 
storing, in time of plenty, supplies that might be drawn 
upon in seasons of want. And stored products of all kinds 
have ever been attractive to those insects that feed upon 
dead animal or vegetable matter; not necessarily decay- 
ing or decomposing matter, but simply that which is 
without active life and ready to return to its original con- 
stituents, whether by way of the human alimentary canal 
or in any other manner. Stored seeds are not dead in the 
strict sense of that term; but it can stand here for that 
inactive condition of vegetable life in which it is not ca- 
pable by any process of growth of outrunning or opposing 
the attacks of such creatures as attempt to feed upon it. 

There is no one species of insect that is confined to 
human habitations. All are species that also occur under 
normal outdoor conditions, and that could continue even 
though every trace of mankind were removed from the 
face of the earth; but as to some of them the straggle 
would then be very seriously intensified. 

We might arrange the species that associate with 
man so closely, in the order of the manner in which 
they afi'ect us, and that would be the better method 
were we intent only on a treatise dealing with house- 
hold pests; bt:t I have preferred to follow the general 
scheme of dealing with the orders and giving those 
general habits that have indticed certain of their mem- 
bers to frequent man's neighborhood. 



2l8 



INSECTS 



I begin by stepping outside the insects altogether 
and deahng with the common house "centipede" or 
"thousand legged worm." It is a frail yet formidable 
looking creature with a large 
number of long slender legs, 
yellowish-gray in color and 
mottled with blackish. It has 
a pair of long, many-jointed 
feelers and the last pair of 
legs are unusually extended 
so that they give a weird im- 
pression of danger that makes 
most people hesitate about in- 
terfering, except through the 
agency of a broom or similar 
weapon. It is most commonly 
seen in cellars or on damp 
walls, but may occur almost 
anywhere in the house, and 
its mission is quite innocent; 
praiseworthy in fact, for it is 
predatory on other household 
insects, feeding on roaches, 
bed-bugs, moths and such sim- 
ilar creatures as it is able to 
get hold of. The specimens 
should really never be inter- 
fered with at all ; but few per- 
sons like their looks and there 
is neither danger nor difficulty 
in killing them. At a touch 
the thing collapses into a struggling mass of legs, which 
continue to wiggle for some little time after they are 
separated from the body. The natural habitat of 
species of this kind is under the bark of trees, under logs 




Fig. ioi.— a house centipede, Scm- 
tigera forceps. 



RELATION TO THE HOUSEHOLD 



219 



or in other damp, sheltered situations. There is a small 
poison gland connected with the mandibles which, how- 
ever, are incapable of piercing the human skin. Nor is 
the poison sufihcient in quantity and character to cause 
any appreciable trouble, even if by any combination of 
circumstances the jaws could be forced into the flesh. 

Among the true insects the lowest or most primitive 
order, the Tkysanura, are represented in houses by 
several species. In the cellar 
of the farm-house where veg- 
etables and other provisions 
are stored in quantity, they 
occur wherever it is damp 
and wherever the least sus- 
picion of decay occurs. There 
are here several species of 
bristle-tails and spring-tails; 
small wingless creatures, 
soft-bodied, with indefinite 
mouth parts, that feed only 
where a way is opened to 
them by other things; but 
when that way is opened 

their feeding promotes the decay that first gave them 
entrance, and by their numbers they may become 
troublesome. Remembering their fondness for damp 
places the free use of lime and thorough ventilation 
will serve to disperse them. Some are so lowly organ- 
ized that the tracheal breathing system is not fully 
developed and oxygen is absorbed through the damp 
skin. To such creatures dryness is fatal. In cities 
and towns few of these insects are found, and prac- 
tically only two species of "bristle-tails," or "fish- 
moths" or "silver-fish" occur. One of these species 
is quite tough in texture, somewhat convex, evenly 




— A spnng-tail or 
Podurid. 



2 20 INSECTS 

silvery, and found only in cellars or damp places; 
the other is very soft-bodied, the silver mottled with 
blackish or gray, and found in dry warm places Hke 




Fig. 103. — The silver-fish, Lepisma domestica 



kitchens, bake-houses and pantries. They feed on 
all sorts of starchy products and nibble preferably at 
bits of bread, cake and the like; but at a pinch they 
gnaw the calendered surface of paper or book bindings, 
and have been known to attack the glossy surface of a 



RELATION TO THE HOUSEHOLD 



shirt front. They are rarely abundant enough to be a 
real nuisance, and wherever it is necessary to deal with 
them they yield readily enough to pyrethrum or gaso- 
line whichever may be indicated; naphthaline serves 
very nicely as a repellent wherever one is necessary. 
Ordinarily, killing the specimens as they come under 
observation answers every purpose. 

A little higher in the scale of development come the 
"book lice" belonging to the family Psocidcz, allies of 
and somewhat resembling the 
biting lice that have been al- 
ready dealt with in their rela- 
tions to other animals. Indeed, 
as a rtile housekeepers when 
they notice these little insects 
among their stores of linen or 
in dusty corners of drawers, 
suspect them of being really 
parasites or true lice. But all 
lice, whether of the biting or 
sucking variety, are awkward, Fig- 104.— a book louse, 
slow- moving creatures on a 

level surface, w-hile these little Psocids are active and 
agile, running backward or forward with equal readi- 
ness, and so spry as to be not easily captured. When 
captured, instead of being tough and leathery in texture, 
requiring an effort to crush, they are soft and go to 
pieces at a touch. They are never found on animals of 
any kind, and what they are after is the little organic 
particles that they get from any sort of dry animal or 
vegetable matter. A dead fly will be reduced to a fine 
powder by them in a few days when they are abundant, 
and in collections they are occasionally something of a 
nuisance; but almost any pungent odor drives them 
away, and besides we have always the resource of not 




222 INSECTS 

leaving anything about that is attractive to them. 
Camphor, naphthahne, oil of sassafras, carbolic acid, 
and oil of peppermint have all been employed with good 
effect and, really, almost anything answers. Occasion- 
ally they infest an old straw or corn husk mattress in 
great numbers, and in such case the only real remedy is 
the fire. Other members of this group composing the 
order Corrodenlia or "gnawers," a branch of the great 
Neuropterous series, are winged and live outdoors, as 
indeed do many of the wingless species; but always 
their food is dried animal or vegetable matter, so that 
the only reason why any species occurs in our houses is 
that the materials that they feed upon are found there. 
Scarcely higher in development so far as structure 
is concerned are the Termites, or "white ants;" but 
though low in physical organization they are most 
wonderfully developed en the social side, standing 
scarcely inferior to the true ants. Termites are not 
numerous in species anywhere in temperate or frigid 
North America, and throughout most of our country 
only a single species occurs or is at all common — the 
Termes fJavipcs. In warmer countries and in the trop- 
ics, the number of species is much greater, while in 
Africa they have their point of greatest development. 
In that country the insects themselves are house build- 
ers, their habitations rising in many cases ten feet or 
more above the surface in turret-like form and clustered 
in great villages. But it is not with their peculiar or- 
ganization nor interesting social life that we have to do 
here; but with their habits when they leave their own 
dwellings and invade ours. Yet to fully understand the 
creatures and how they come to be with us at all, we 
must know a little of their history. The popular term 
"white ant" is derived from the pale, yellowish-white 
workers of the common species, which are wingless, 



RELATION TO THE HOUSEHOLD 



!23 



about one-fourth of an inch long, flattened, with a large 
head, small thorax and a rather large, ovate, bluntly 
terminated abdomen or hind body. Outdoors they are 
usually found in small numbers under fiat stones at the 
edges of woods, in fallen trees, old stumps or in woody 
material generally. When a colony is disturbed most of 
them will dive out of sight into galleries underground 




Fio. 105.— Termes -fiavipes. — a. larva; f>, winged male; c, worker; d, soldier; 
e. female; /, pupa. 



and seem to be concerned only in getting away as fast 
as possible. They are very soft, helpless, without eyes, 
and in the day-light are absolutely defenseless. A few 
specimens a little larger in size will appear bolder than 
the rest, not quite in such a hurry to get away, and when 
we look at these more closely, we note that the head is 
larger and that they have longer, pointed jaws or man- 
dibles. They are indeed the soldiers of the colony, and 
developed for its defense; but very helpless soldiers at 
that when uncovered, because like the workers they are 
wingless and blind. Both workers and soldiers are 



224 INSECTS 

represented in both sexes, but the reproductive organs 
are undeveloped and neither sex is capable of repro- 
ducing. If we get at the home of a large colony in an 
old tree, in late fall or early spring, we may find with 
these white, wingless forms, some decidedly larger, 
rusty brownish specimens, which have well developed 
long wings lying fiat on the back and well developed 
eyes. These are the males and females which during 
the warm days of spring leave the parent nest in a body 
and swarm. They are sometimes seen emerging from 
some old fence-post or house timber in great hordes 
and for a short time fill the air. Their flight is very 
weak, the two pairs of wings being unconnected and 
very similar to each other, and when they have mated 
they disappear. The majority of all these specimens 
die without being able to found a colony and the method 
of starting varies somewhat with the species. For our 
present purpose it will be sufficient to say that in a 
developed colony there is one queen or egg-laying 
female, with abdomen so distended that she is helpless, 
simply oozing eggs which are taken and cared for by the 
workers. Or there may be several " complemental " 
females which have never left the nest and never become 
fully winged. In any case the co,lony consists of many 
thousands of individuals and from the centre, where the 
queen resides, galleries extend in all directions. The 
food is usually wood-fibre ; but may be any sort of dry 
vegetable products even when made up into thread, 
paper or other artificial forms. Because they are blind 
the workers shun the light and always work in burrows 
or galleries, first eating out the fibres as food and then 
using the excrement to form cells or chambers where the 
raw tissue has been removed. When a nest of Termites 
has its centre near a wooden dwelling, the galleries may 
at almost any time reach some of the posts or supports: 



RELATION TO THE HOUSEHOLD 225 

and when they do, the insects work into and through 
the wood in concealment, until suddenly there is a 
collapse. In the tropics they get into floor boards and 
the furniture resting on it, always mining out of sight 
until there is a breakdown. 

Where the insects are plentiful their habits are well 
known and house builders use all sorts of precautions to 
keep them out and never leave furniture in one place 
very long. In the more northern countries where T. 
flavipes only occurs, or is the only common species, 
usually fence- or stair-posts only or the timbers of 
bams and other out-buildings are attacked and then 
the problem is getting at and destroying the central 
nest, which is usually in an old stump or log not far 
away. Only occasionally do they get into the beams or 
timbers of dwellings or other inhabited buildings; but 
when they do, they usually work until the timber is 
ruined before their presence is suspected. In such 
cases there is nothing to do but remove the infested 
material and put in iron or, before putting in another 
wooden support, treating it with some creosote or other 
poisonous preparation unless the central nest can be 
found and destroyed. They have been known to get 
into a store-house and to ruin large quantities of sup- 
plies before their presence was even suspected, and 
into a masonry vault containing records, leaving the 
pile of books and records fair to all outward seeming, 
but a mass of cells and excrement behind it. 

Yet a little further up come the members of the 
order Orthoptera, including some of its most unlovely 
fellows, the roaches; but also a few that have appealed 
more to poets and dreamers in the chimney corner — 
the crickets, including of course those on the hearth. 
Crickets are generally accidentals and their presence is 
usually due to their search for shelter. They are suflEi- 
15 



226 INSECTS 

ciently catholic in their tastes to exist for some time on 
such scraps as they can find indoors and so the cheerful 
chirp is not infrequently heard in some country locali- 
ties. But there are other species, with other habits. 
In sandy districts and often along the coast where 
crickets are very abundant outdoors, they are apt to 
get into houses in their general wanderings and develop 
an inordinate fondness for woollen goods, especially if 
the}' are at all damp. It has been my fortune to accom- 
pany a fisherman on an early spring trip to the club- 
house at the seashore, after it had been closed since the 
preceding fall, and I watched him open the drawers of a 
bureau containing his store of clothing, and then I 
listened to his expression of regard for the crickets 
that had found the garments so toothsome; and I 
grinned in no holy joy, for that same fisherman had 
always regarded insects as unworthy of consideration, 
and knowledge concerning them as of no account what- 
ever. And lo, now he was forced to appeal to that 
knowledge and ask advice! It was all very easy and 
meant simply have everything perfectly dry when put 
away, and have things put into a trunk or chest rather 
than a drawer. Where crickets do get annoying, pieces 
of soft bread dusted with Paris green or white arsenic 
will soon rid the house of them. 

As for roaches, there are a few that have been dis- 
tributed by commerce throughout the civilized world 
and, in addition, some localities have species of their 
own which, while living chiefly outdoors, rather com- 
monly get indoors as well. In the tropics roaches are 
most numerous, and in the warmer parts of our own 
country even the common species are more abundant 
and troublesome than they are further north. 

All roaches have much the same appearance and 
general habits. They are flattened, soft-bodied with 



RELATION TO THE HOUSEHOLD 



227 



long spiny legs, long slender feelers, and the head bent 
down so that the mouth comes almost between the 
front legs. Some are winged and some are not; but 
even the winged species do not as a rule fly readily and 
some never at all. They hide in crevices during the day 
and roam abroad at night seeking what they may de- 
vour, and they are not at all particular what it is; dry 
scraps of animal matter, moist vegetable matter — almost 
anything indeed that can be eaten. Moist articles are 




Fig. io(). — The "Croton bug," Ectohia gcrmanica: a. first; b. second; c. third; 
d, fourth stage; e. adult; /.female with egg case; g, detached egg-case; h, adult 
with wings spread. 



preferred and a warm wet dishrag which was not w^ashed 
after using has almost irresistible attractions. If there 
was only one roach in a kitchen and I wanted that roach 
I would place just such a rag on the middle of the floor 
soon after dark, and I would expect that roach there 
before ten o'clock. This applies more particularly to the 
large oriental roach or "black beetle" which is very 
heavy, does not climb much, and prefers moist places. 
The "croton bug" or "German roach" is a much 
smaller species, climbs readily, and favors drier places. 
It is much bolder than the oriental species, and is not 
infrequently seen during the day. 



228 INSECTS 

How to get rid of roaches is a question frequently 
asked, and judging by the number of infalHble roach 
powders and foods on the market is one frequently and 
satisfactorily answered. Most of the dry powders 
depend on a mixture of sugar or chocolate with borax, 
the latter being the killing agent, ihe sugar or chocolate 
merely to attract. Mix equal parts of sweet chocolate 
and borax in a mortar, so as to mingle thoroughly, and 
spread where roaches abound, removing, so far as 
possible, all other food particles. 

Roach pastes usually contain phosphorus or arsenic 
and are applied on pieces of soft bread which is a favor- 
ite food. An ingenious Australian scheme is to mix 
one part of plaster-of-paris with three or four parts of 
flour and set it on a small saucer easily accessible to the 
insects. Feeding on this makes the roaches very thirsty 
and they seek water; dishes of this should also be 
placed near by and when this is added to the flour and 
plaster, the latter sets and clogs the intestines. This is 
a very simple, safe and inexpensive method, and once 
the flour and plaster are set out, needs only attention 
to keeping up the supply of water. In any case when a 
house is once badly infested by roaches and it is desired 
to clean them out, it mteans a campaign. No one appli- 
cation will ever be successful, but persistence will be 
victorious in every instance. 

There are many interesting peculiarities about 
roaches, but none greater than their egg-laying habits. 
The entire egg supply of the female develops simul- 
taneously in a sac or case attached at the end of the 
body, technically known as an ootheca. As the eggs 
develop this case enlarges, until all have attained full 
size and the eggs are almost ready to hatch. Then the 
female drops it in some sheltered comer, the seam along 
one side splits, and all the young roaches come out at 



RELATION TO THE HOUSEHOLD 



229 



about the same time. As a matter of policy it is always 
well to begin a roach campaign before the egg cases 
have been fully developed, as there are then much 
fewer specimens to be dealt with. 

The Hemiptera as an order are always difficult to 
place in a linear series among the mandibulata, but 
thev contain one species that must be referred to among 
the forms dwelling with man — the "bed-bug," Cimex 
lectidarius. It has local names in different parts of the 




Fig. 107. — The bed-bug from above and below and egg. 



countr}', but "bed-bugs" are always recognized even 
where they are commonly referred to as "chinches." 
There are quite a number of the Hemiptera that are very 
much flattened and fitted to live in narrow crevices; 
but none more than this bed-bug which occurs now-a- 
days only in connection with human habitations. An 
allied species lives in the nests of swallows, sometimes 
in great numbers, but does not infest houses. 

The pest is found all over the world and has been 
recorded ever since there were any records; so there is 
an immense fund of information concerning it — some 
true, some more or less imaginary, like the tales of the 



230 INSECTS 

ingenious measures adopted to reach sleepers in beds 
which had been isolated so that the}^ nowhere touched 
the wall and had the posts set in pans of water. The 
bugs are normally red brown in color, but when first 
hatched or when compelled to go without food for a 
long period, they are almost transparent whitish. 
Just how long they can go without food seems to be 
not definitely determined, but it is certain that houses 
entirely uninhabited for a year have been found infested 
with very hungry bugs when again put to use. The 
insects moult five times and normally feed only once 
between moults, a period of five or six days. Nor, 
when the insects have fed, do they always or even usually 
stay in the bed occupied by the victim. On the con- 
trary, especially where there is a metal bed, they are 
very apt to leave it and seek some other piece of furni- 
ture or get behind base-boards, picture mouldings, 
trimmings or even behind the backing of picture frames. 
In one case the resort for a considerable colony was 
found in the large old-fashioned lock on the room door. 
In the large wooden bed of the older type there was 
usually abundant chance to hide and these beds were 
difficult to get and keep clean, especially before the days 
of gasoline. In such cases a large percentage of the 
bug population might be confined to the bed; but the 
life of the "chinch" becomes ever more difficult under 
modem conditions, and with a little care, practical 
exemption is securable in a well-ordered household. 
Their occasional introduction is almost unavoidable 
where public conveyances are used. I have seen them 
in railroad cars, trolleys, boats, omnibuses and carriages, 
and have noted them crawling on the clothing of well- 
dressed fellow passengers who probably did not bring 
them in. It means, therefore, in the average house- 
hold, a more or less continual vigilance on the part of 



RELATION TO THE HOUSEHOLD 231 

the housekeeper, and one of the first and most charac- 
teristic signs of their presence is the round black spot 
produced by their excrement on the bed hnen or other 
places where they have rested. Some extremely sen- 
sitive persons recognize their presence by the pecuHar 
buggy odor, which is not ordinarily noticeable until the 
insects are handled. Eggs are laid in the crevices in- 
habited by the adults, in small batches, and oviposition 
extends over a considerable period. They are whitish, 
oval, reticulated, and, like most hemipterous eggs, of 
rather large size, so that they are easily seen and recog- 
nized. The total life cycle, from egg to adult, is about 
forty-five days, and the insects do not breed during the 
winter, except under unusual conditions. 

Given an ordinary infestation in an ordinary bed- 
room, thorough work would mean taking out all bedding 
and taking apart and examining the bed. With a large 
bulb pipette force gasoline into every crevice however 
small, and drench the binding and tuftings of the mat- 
tress, wherever there is a folding over that might serve 
as a hiding place. Force gasoline through the pipette 
behind and under the base-boards, under the picture 
moulding, behind all the trim of the room, and into all 
other possible hiding places. Treat the wash-stand, 
bureau and all other furniture to liberal doses, and 
carefully examine all pictures for signs of either eggs or 
"spots." If necessary remove the back to see whether 
the insects have made their way under it. The gaso- 
line will kill every insect it touches; but not the eggs, 
so that a second treatment must be made to reach the 
insects that hatched after the first. It will require 
about one gallon of gasoline for a bedroom of good 
size, with a normal amount of furniture, and the ma- 
terial will hurt neither fabrics nor paper. Bad infesta- 
tions in hotels, boarding-houses or tenements are best 



232 INSECTS 

reached by fumigation with hydrocyanic acid gas, 
which will be described later on. 

In the southern and southwestern states there is 
another, much larger species that has also developed 
the house habit and is known as the "big bed-bug," or 
the "blood sucking cone-nose," Conorrhinus sanguisu- 
gis. It belongs to the family ReduviidcB or "assassin 
bugs," all of which are predatory in habit, and its bite 
is a serious matter, causing much swelling and often 
inflammatory and febrile symptoms. These insects 
are so large and so little fitted for hiding that ordinary 
care in looking after beds and rooms will detect them 
and prevent trouble. 

Among the Coleoptera or beetles there are a large 
number that live with us and cause trouble. All, how- 
ever, are species quite capable of taking care of them- 
selves outdoors and come to us only because we have 
in our possession or in the building some of the products 
upon which they normally feed. 

A good illustration is found in the species belonging 
to the family DermestidcB, nearly all of which are feeders 
upon dried animal products. The term "dried animal 
products" is a broad one and includes little scraps of 
meat left on an old bone, a bit of hide remaining where 
an animal has decayed, or a pile of hair or wool, no 
matter where found. A dead insect found in the field 
serves as a nidus in which an egg is deposited, and if 
the dead insect is in our collections that is not a matter 
of concern to the beetle, provided it can be gotten at. 
We have, therefore, larder beetles, leather beetles, 
museum beetles, carpet beetles, and a variety of others 
of the same type, all seeking in our dwellings that dried 
animal food which they require, and whose presence is 
indicated to them by the discriminating sense of smell 
with which they are fitted. 



RELATION TO THE HOUSEHOLD 



233 



All the members of this family are dull brown or 
blackish, clothed with gray, white or colored scales ar- 
ranged in more or less distinctive patterns. They are 
more or less oval, without conspicuous head, and with 
short legs and feelers that can be retracted and folded 
close to the body, so that the insect, playing 'possum, 
looks like a bit of dirt or other fragment among the 
mass in which it lives. The larvae or grubs that do the 
real damage are stumpy, worm-like creatures set with 
brown hair, often with a longer 
brush at the end of the body, 
sometimes with a series of tufts 
at the sides. 

The carpet beetles are best 
known and least liked of all 
these species, and in the adult 
stage when they frequent the 
flowers in our gardens, are 
rarely recognized. The so- 
called "buffalo-moth," in the 
adult stage, is really very pret- 
ty, with its lines of brilliant 
red and white scales. This in- 
sect is a feeder on animal hair, and that accounts for 
its attacks on woollen goods and feathers. Its close 
ally, the black carpet beetle, has similar habits, and 
both sometimes get into a feather pillow and create 
havoc. Where the cover to the pillow is of the right 
texture, the feather fragments are occasionally worked 
into it so as to form a soft, felt-like covering, that 
puzzles the enraged housekeeper when she discovers 
the condition of her feather stufifing. All woollen and 
feather fabrics are attacked and fed upon, and the 
best way to prevent trouble is to keep those things 
not in actual use shut up until midsummer. A.fter 




Fn;. loS.—c. I lie larder bee- 
e; a. its larva; h, larval hair. 



234 



INSECTS 



that there is no further danger from these species. 
Of course the usual repellents, camphor, naphthaline 
and the like are useful, and gasoline is an excellent 
destructive agent; but after all, care and protection by 
tight boxes or paper bags is best. When carpets on 
the floor are attacked and it is not convenient to take 
these up, a liberal use of gasoline is indicated, until no 
further traces of the insect work are noted. 




Fig. 109. — d. the carpet beetle/ a, its larva, the "buffalo moth' 



Almost every museum and every collector of speci- 
mens of organic natural history has to do with two or 
three species that attack such dry products by prefer- 
ence, and here again the ordinary repellents are brought 
into use, supplemented by a free use of bisulphide of 
carbon, ether or chloroform. None of these is advisable 
in ordinary household use because of either expense or 
danger, so there is no necessity for going into details. 
The larger species such as the larder beetles are usually 
controlled by screening or keeping the provisions prop- 
erly covered. The leather beetles that occur more 
commonly in manufacturing establishments must be 



RELATION TO THE HOUSEHOLD 



235 



dealt with according to the conditions as they exist in 
each individual case. 

Quite a different series of species attack our stored 
grains and other vegetable products. The largest and 
most conspicuous of these are the meal worms — long, 
vellowish, slender worm-like grvibs with a brown head 




e 

Fk;. 1 10. — a. the meal worm; b. pupa; c. adult beetle, Tcncbrio molitor; d, its egg; 
e, antenna. 



and anal segment, reaching the length of an inch or 
more. These live in meal of all kinds and are more 
common in the barn and stable than in the house 
though not unknown there by any means. The parents 
are oblong flattened black beetles nearly three-quarters 
of an inch in length, and are usually found in the same 
places as the larva?. Incidentally these meal w^orms 
are great favorites with our feathered friends, and they 
are raised in great quantities as food for cage birds of 
various descriptions. 



236 



INSECTS 



Allied in appearance but very much smaller, come 
the various species of flour and grain beetles; the larvae, 
very slender whitish grubs, not much over an eighth of 
an inch in length, the adults equally slender, flattened 
brown beetles, less than that length, or scarcely attain- 
ing it. They accumulate wherever meal or grain prod- 
ucts of any kind are kept open and allowed to stand for 
any length of time. In pantries or closets where jars or 




-The confused flour beetle, Tribolimn confusum: a, adult; b, larva; 



receptacles are never entirely cleaned out before re- 
plenishing, they find their best opportunity for multi- 
plying, and the best method of checking them lies, in 
consequence, in cleaning out thoroughly every recep- 
tacle for such products before putting in a new supply. 
In peas, beans, lentils and the like, "weevils" often 
make their appearance, and that is manifested when in 
such seeds one or more round holes about one-sixteenth 
of an inch in diameter may be noted. Now while, ordi- 
narily, these insects breed outdoors, and simply pass the 
winter in the seeds that were attacked in the field ; yet 



RELATION TO THE HOUSEHOLD 



37 



in the artificial warmth of our houses the beetles emerge 
in late fall or during the winter, and lay their eggs on 
the dried peas, etc., so that what may be a pretty fair 
lot of legumes in fall, may be an utterly useless lot of 
vegetable debris, in the spring following. The grubs 
in this case are chunky, white creatures, curled up 
inside the seeds, and the beetles are small, very chunky 
gray forms, with very stout hind legs and the hind part 
of the abdomen very abruptly terminated. The ordi- 




/■ W #P 





Fig. I 12. — The drug beetle, Sitodrcpa paniccc: a. larva; b. pupa; c. d. adull. 



narv householder sees little of them because, as a rule, 
only a small stock of such products for almost imme- 
diate use is at hand; but to the fanner, the seedsman, 
the grocer or other dealer, the matter is sometimes 
serious. Fortunately wc can reach the insects even 
inside the seeds by the fumes of bisulphide of carbon, 
in a manner to be pointed out a little later. 

Then come those species that get into more solid 
vegetable fibre, like roots, stems or even wood, and 
many of these belong to the little family Ptinidcs which 
contains a mixture of odd and bizarre forms, very 
dififerent and yet very similar in general character and 



238 INSECTS 

habits. The drug beetles, Sitodrepa panicea, and the 
cigarette beetles, Lasioderma serricorne, are examples of 
such forms and, in the adult stage, are little, brown, 
more or less cylindrical species, not much if any over 
one-tenth of an inch in length. The eggs are laid in or 
on almost any kind of wood or leaf tissue, and the larvae 
which are very small, curved, white grubs, bore into this 
tissue reducing it to powder. Cigarettes, cigars and 
plug tobacco are often attacked and little round holes 
through the surface tell the tale of the destroyer. So 
the roots of licorice and hellebore are equally favorites, 
and may be reduced to powder, while occasionally 
willow- and rattan-ware is seriously injured. 

The somewhat larger species of Hadrohrcgmns, and 
the species of Lyctus or powder post beetles belonging 
to the same family, occur in the woodwork of houses 
or in furniture, and may create serious trouble. They 
live and bore in the seasoned wood, mining it in every 
direction and in time reducing it to a mass of powder. 
Little round holes, from which sometimes little masses 
of sawdust are ejected, declare the character of the 
insects at work here, and for them there is no one 
method of treatment. Creosote, gasoline, tar, paint 
and similar penetrating or covering mixtures are ap- 
plied with more or less good effect, and which of them 
is to be used depends upon the especial conditions of 
the attack. 

In the order Lcpidoptera, the "clothes moths" have 
become adapted to a life in our dwellings and are rarely 
found elsewhere. They belong to the great group of 
Tineid moths in which the early or primitive characters 
of the order are yet well marked, and as a relic of their 
ancestral habits they retain the practice of making cases 
or shelters in the larval stage. This serves as a protec- 
tion to the caterpillar and as a means of concealment; 



RELATION TO THE HOUSEHOLD 



239 



for being made of the material among which the insect 
feeds, it is not usually conspicuous. The divergence 
from the usual vegetable feeding habit of caterpillars 
is a specialization that is quite marked, because it is 
not only a feeding upon animal tissue but upon dried 
or dead animal tissue. In Chapter VII it was pointed 
out that some moths lived in the heavy fur of certain 
animals so that they became literally moth-eaten dur- 
ing their lifetime, and this habit of feeding upon such 




Fic. 1 13. — A clothes moth. Tinea pcUionclla, with its caterpillar in and 
out of case. 



material when removed from the animal is only a little 
further specialization in the same direction. It fur- 
nishes, also, an explanation of why woollens and ma- 
terials made of animal hair or fibre, in whole or in part, 
are subject to moth attacks, while linens and cottons 
are practically exempt. 

The "moth" itself, or "miller," is a small, glisten- 
ing, light yellow creature, with very slender, long 
fringed wings, and it may be seen fluttering about in 
the dusk of early evening in our rooms during late 
spring or early summer. If when a closet door is opened 
at this period a number of these moths flutter out, 



240 INSECTS 

there is a probability of damage already caused, and 
very great danger of more damage to come. Not that 
this moth itself has done or is capable of doing any 
injury. Its mouth parts are such that it is practically 
incapable of feeding at all, and altogether incapable of 
feeding on solid tissue of any kind. But it lays its little 
whitish eggs in the woollen or similar tissue wherever it 
finds a chance to do so, and from these eggs hatch the 
little caterpillars whose mouth parts are formed of 
sharp jaws, quite fitted for cutting the animal fibres 
among which they live. Almost the first work of the 
caterpillar after hatching from the egg is to form a 
little case from the tissue among which it finds itself, 
held together with silken threads of its own produc- 
tion; and this case is enlarged from time to time as the 
insect grows. It is curious how these individuals differ 
in habit. Sometimes the cases will be made up of fibres 
of all colors, indifferently put together without pattern 
or system. At other times, and that is rather the rule, 
the color first selected will be adhered to, so that in a 
carpet one pattern may be completely eaten out, while 
others, of a different color, will be untouched. In my 
own experience I have observed a very decided prefer- 
ence for reds where such were obtainable, and in rag 
and brussels carpets I have seen the red stripes and 
flowers eaten, while the blue stripes and green leaves 
were untouched. 

The period of development depends on the tem- 
perature. In the more northern United States there is 
only a single brood; in the middle and southern states 
there are two and in the extreme south and on the 
Pacific coast there may be more. But the insect is 
sensitive to cold and does not grow or develop unless 
the temperature is above 60°, even though it is not 
killed by a much lower degree. Hence has come the 



RELATION TO THE HOUSEHOLD 241 

practice of placing furs and other valuable articles of 
apparel or drapery in cold storage where, even if already- 
infested, no development can take place. The ento- 
mologists of the U. S. Department of Agriculture 
have determined that a temperature of 40° is low 
enough to prevent any development, and my own 
experience in the household is that until a daily average 
of 60° is reached, little danger is to be apprehended; 
but this, of course, does not mean that in closets so 
placed that a higher average temperature is main- 
tained, breeding would not go on even though the 
outside temperature was not above 60°. 

To prevent infestation, nothing is better than to 
brush all the clothing to be protected and then pack it 
into tight boxes. They need not be heavy nor large 
boxes, but they must be tight. Pasteboard boxes will 
answer every purpose if the covers are fastened at the 
point of junction with gummed strips and such boxes 
are now obtainable of almost any size, for garments of 
all kinds. Heavy paper bags answer the same purpose, 
and these are now sold for that purpose in the larger 
cities. They can be easily made where they cannot be 
bought. Even carefully wrapping in newspaper, using 
plenty of paper and covering joints, will answer, where 
the garments are packed away in trunks or moderately 
tight drawers. But there should be no doubt about the 
freedom of the garments thus put away from "moths" 
or their eggs. When a fabric is once infested and the 
insects cannot be reached by beating or brushing, a 
drenching with gasoline is effective, and when a closet 
becomes infested, it should be thoroughly sprayed with 
gasoline so that every crevice is reached and penetrated. 
Fumigation with sulphur will kill them if properly made, 
but there must be no metal and no fabrics in the closet 
when it is done. Formaldehyde vapor is ineffective. 
16 



242 INSECTS 

As for the various repellents like camphor, naphthaline, 
tar, etc., these are all of some value and in proportion 
to the tightness of the drawer, trunk or other recep- 
tacle in which they are used; but none are implicitly 
to be relied upon if the fabric is already infested, or if 
the container is not reasonably tight. Gasoline will 
kill every caterpillar that it touches and is the best 
material to use where rugs, carpets, hangings or drape- 
ries that cannot for any reason be removed are to be 
dealt with. 

We have further, among the Lepidoptera, and in 
this same group of Tineids, other moths and their 
larvas that feed on our stored products, but hardly in 
our houses, and such are the Indian meal moth, Plodia 
inter punctella, the Angoumois grain moth, Gelechia 
cererella, the meal snout moth, Pyralis farinalis, and the 
like. They scarcely come under this head for detailed 
consideration; but should be mentioned to call atten- 
tion to the fact that they may be found among products 
often stored yet hardly to be considered as inhabi- 
tants of the household itself. 

In the order Hymenoptera the ants are not infre- 
quent invaders of our domestic economy. Sometimes 
they come in merely on exploring expeditions from 
outside, with no thought of remaining. It is merely 
part of the htmt for food, and if something is found, a 
squad is soon at hand to clean it out. Among such 
visitors comes the large black carpenter ant, which 
nests in partly decayed logs, branches of trees and the 
like, and forages for a considerable distance round about. 
A house near a large nest is likely to be so frequently 
visited as to make them a nuisance, and to abate this 
the colony should be located and their home destroyed. 
This general recommendation applies to any species 
which comes in as a visitor in this same way. 



RELATION TO THE HOUSEHOLD 243 

Sometimes ants make their nests just outside of our 
houses, on the lawns, and while this does not bring 
them strictly under this chapter head, we may digress 
for a moment to consider them as a nuisance. With a 
cane or other stick poke a few holes to the depth of 
about ten inches near and about the centre of the nest, 
and into each hole pour about one ounce of bisulphide 
of carbon, covering the hole by stepping on it. The 
fumes will penetrate throughout the galleries and kill 
all the ants and their larvae that are 
reached. Usually one application is 
enough; if by any chance there is 
renewed activity about the nest a few 
days later, repeat the application. 

Within our houses three or four 
much smaller species make their 
homes, and establish colonies. There 
is a small red ant, a larger black ant, 
a very small black ant and, more ,„r;y;,t~t'°::: 
occasionally, a very small red ant. pharaoms. 
They differ materially in their habits 
and somewhat in their Hfe cycle, but for our purpose 
are enough alike to be considered together. Like all 
ants the colonies consist of a queen, a large number of 
workers and, in the late summer and early spring, also 
the males and females that will at the proper time 
leave the nest to swarm. Only the workers are seen as 
a rule, and these swarm over everything in the nature 
of food, and cart it off to their nests which are situated 
behind base-boards, in crevices behind the plaster or in 
the masonry, or anywhere in the shell of the house where 
they can establish themselves. Once a house is thor- 
oughly infested the task of getting rid of them becomes 
a serious one and can be accomplished only by persistent 
work ; but it can be accomplished. In the first place lo- 




244 INSECTS 

cate the nests if possible and destroy by injecting gaso- 
line or bisulphide of carbon with a syringe. Both of these 
are highly inflammable and should only be used where 
there is no fire nor open artificial light of any kind. 
Many colonies may be reached in this way and greatly 
weakened or destroyed. Others will be so situated that 
they cannot be reached, and the insects will simply seek 
less exposed openings into the rooms. The systematic 
campaign then consists of keeping all food products un- 
der cover so far as possible, or protected by belts of cre- 
osote or oil of lemon, which the insects will not readily 
cross. Set out, easily accessible in their ordinary lines of 
march, all the raw bones with small particles of adher- 
ent meat that come from the kitchen, and when these 
become covered with ants throw into the fire and 
burn. Or with a knife scrape the surface of a piece of 
meat and spread the scrapings thinly on a piece of 
paper. Bum this when covered, in the same way, 
always taking care to let none escape. Keep this up 
consistently and persistently, and no matter how 
numerous the ants may seem to be, they will become 
so greatly reduced in numbers that the nests are dis- 
organized for lack of workers. There will be no one to 
feed or care for the young and the colonies will perish. 
Instead of the meat and bone method the sugar-sponge 
method may be employed. This means two moderate 
sized sponges, saturated with sugar water and pressed 
nearly dry. Place one near the run until the ants 
swarm in all its cells; then remove and drop into boil- 
ing water, substituting the second sponge in its place. 
The boiling kills the ants, of course, and the sponge 
should then be thoroughly washed to get rid of the 
dead insects, again dipped into the sugar water and 
prepared to replace the second sponge when that is 
ready to be boiled. It is sometimes a matter of weeks and 



RELATION TO THE HOUSEHOLD 245 

it may be necessary to change the location or even the 
character of the traps several times; but, faithfully car- 
ried out, I have never known this plan to fail, and I have 
personally employed it in two houses occupied by me, 
when the insects threatened my collection and ate the 
fresh specimens on the setting boards when not protected 
by carbolic acid belts. This plan is of no avail against 
those ants that come in merely as foragers from the out- 
side, like the black carpenter ants already referred to. 

Of recent years a species of ant has been introduced 
into one of the southern states from Argentina that is 
far more troublesome than any of our American species. 
It bids fair to spread and to become a first class pest so 
far as it extends; indeed it has been already reported 
from California and may be more wide-spread than we 
now believx. It is known as Iridomyrmex hiimilis, and 
is as ready to establish its colonies indoors as out. 
It is under investigation by the entomologists in that 
section of the country and we mav hope that before it 
gets much further, efficient methods for its control will 
have been developed. 

In the order Diptera there are no species that are to 
be considered as guests except the common house-fly, 
and that is dealt with in the previous chapter in its 
relation as a carrier of disease. So the flea, which gets 
into houses not infrequently, does so as a parasite of 
the dog or cat, and not because of any love for man 
himself. Other flies there are in the house not infre- 
quently, but in most cases as scavengers, when at- 
tracted by decaying or fermenting material, hence not 
strictly to be dealt with here. To be sure we have 
"skippers" occasionally, in cheese, especially of the 
odorous sorts, and sometimes in bacon and other fat; 
but they come very decently under the classification of 
scavengers and need not be further considered here. 



2 46 INSECTS 

And now, it sometimes happens that a house or a 
room long neglected gets into such a condition as to be 
almost uninhabitable by reason of insect pests of all 
kinds — from scavengers to parasites — and the question 
arises whether there is any method by which all these 
things can be reached at one fell swoop, or at least by 
two swoops; the second being made necessary by the 
fact that there are always some forms in the egg state 
and not to be reached even by fumigation with hydro- 
cyanic acid gas, which is usually recommended under 
such conditions. 

Hydrocyanic gas is formed by the action of dilute 
sulphuric acid upon cyanide of potassium, and is one of 
the most penetrating of poisonous vapors, fatal alike to 
man and insects and even to plant life when long enough 
exposed to it ; but harmless to fabrics and not injurious 
to metals. The formula for each loo cubic feet of space 
to be treated, is 

Cyanide of potassium, 98° pure, by weight. . i ounce 

Sulphuric acid, sp. gr. 1.83, by measure 2 ounces 

Water 4 ounces 

Break the cyanide into small lumps and put the 
necessary amount in a thin paper bag. Put the water 
into a glazed earthenware vessel — a wash basin, slop jar 
or other bowl w^ill answer— then add the acid slowly. 
The water will heat as the acid is added and will fume 
or bubble. When all the acid is added, drop in the bag 
containing the cyanide and get out. The formation of the 
gas will be retarded for a few moments while the acid 
gets through the paper and this will give opportunity to 
close the door and seal it as tightly as possible. The 
order of doing this is important, for if it were attempted 
to pour water into the acid, the first drops would cause 
a boiling so violent as to spatter the entire volume in 



RELATION TO THE HOUSEHOLD 247 

every direction. It is also well to have the vessel large 
enough to hold at least twice the amount of liquid 
required, and if more than one pound of cyanide is 
necessary, it is better to have two or more jars. 

Where only a single room is to be treated make it as 
tight as possible by sealing windows and other exits, 
but open all closets, furniture drawers and trunks so as 
to give free entrance to the gas. When the exit door is 
closed, place a damp towel or other cloth at the bottom, 
plug the key-hole with cotton and leave the room 
tightly closed for at least two hours. Then open a 
window or transom from the outside into the open air 
or into a well-ventilated hall, and allow the gas to 
escape for at least ten minutes before entering the 
room. Open all windows for at least an hour before 
attempting to re-occupy the chamber. 

W^hen an entire house is to be treated, first of all 
close and seal all windows and openings to the outer 
air as tightly as possible, except those through which 
the operators expect to leave, and those should be on 
the ground floor. Put into every room and into every 
hall the basins or jars containing the necessary amount 
of water; place alongside in a bottle or tumbler the 
necessary amount of acid and in a bag the cyanide. 
Begin at the top of the house, because the gas is light 
and rises; first pour the acid into all the jars, then add 
the cyanide and repeat on the floors below until the 
entire building is treated. Two men can work better 
than one in a building of any size, and in such cases the 
number of fumigating vessels should not be multiplied 
more than absolutely necessary. If everything has been 
properly prepared it is a matter of only a few minutes 
to start fumigation in a building of considerable size, 
and such a building should then be kept tightly closed 
for twenty-four hours if possible. At the end of that 



248 INSECTS 

time no living creature not in the egg state will remain, 
and the house can be opened to admit fresh air and 
permit the escape of gas. If windows can be opened 
from the outside or a through draft can be obtained, a 
few minutes will answer, and if a scuttle can be opened 
from the roof, the entire house will be safe in half an 
hour if all the doors in the halls are open. 

The directions for use here are much more formi- 
dable than the actual work ; but the danger to life is so 
great if proper care is not exercised, that undue pre- 
cautions are recommended rather than general direc- 
tions that might promote carelessness. 



CHAPTER XI 

THEIR RELATION TO THE FARMER AND 
FRUIT-GROWER 

It was emphasized in another connection that insect 
species that are naturally abundant are so because 
they have made good their position and relative num- 
ber as against all their checks, and so long as natural 
conditions prevail they will maintain that abundance 
with such slight seasonal variations as may be caused 
by temporary favorable or unfavorable conditions. 

When civilized man enters the field, serious changes 
in environment are produced and these changes are 
produced faster than the insect and other life can adapt 
itself to them. In a decade a wilderness is transformed 
to a farm or an orchard, and the balance which it has 
required centuries to establish is rudely upset. Those 
species so nicely adjusted to their surroundings as to 
barely maintain themselves under normal conditions 
may be completely crowded out by the destruction of 
some one factor that permitted survival, and, on the 
other hand, conditions may be changed to favor such a 
species, so as to permit it to increase out of all propor- 
tion to its past history. 

The Colorado or lo-lined potato beetle, universally 
known as the "potato bug," Doryphora lo-lineata, was 
not always the pest that it is at present. When first 
discovered in the foot-hills of the Rocky Mountains it 
was accounted rather a rare species, that barely main- 
tained itself on the scattered indigenous solanaceous 
plants. But when civilization brought in the cultivated 
potato, the species that had been so rare that it had 
249 



250 



INSECTS 



practically no specific natural enemies, found condi- 
tions so materially changed in its favor that it increased 
by leaps and bounds, followed the trail of its food plants 
to the east, and in a few years over-ran the entire area 
of potato cultivation. 

It was first described in 1824; it had become abun- 
dant enough to demand the attention of the economic 




Fig. 115. — Colorado potato beetle: a, egg; b, larvae; c, pupa; d, adult beetles. 



entomologist in 1869, when Riley wrote concerning it 
and the methods to be adopted for its control. I still 
remember the joy that possessed me when, for the first 
time, in 1874, I found on Long Island a patch of pota- 
toes with the insects present in all stages. They had 
arrived earlier, but I had not been fortunate enough to 
get within their range previously. As nature works, 
all this is so very recent that nothing has yet developed 
in the way of an effective natural check. It is rarely, 
however, that an insect is so marvellously favored by 
the changed conditions produced by man. Usually it 



RELATION TO THE FARMER 251 

is a more local species already abundant and vigorous, 
that derives a moderate advantage through the re- 
moval of certain of its natural checks and the greater 
facilities for getting food. 

We must remember that an injurious insect, as 
generally understood, is not necessarily one that seriously 
injures plants, but one that causes notable harm to any 
plant or part of a plant that man wants for his own use. 
The farmer looks with equanimity upon weedy plants 
devoured by slugs or caterpillars, but raises an outcry 
when his cabbages are much less seriously eaten. Yet 
any insect feeding on a cruciferous weed is likely at any 
time to take to cabbage, and so the innoxious species of 
to-day may become the scourge of to-morrow. 

Among the factors that are changed by the farmer 
in favor of the insect, none is of greater importance 
than the elimination of the necessity for seeking a food 
supply. In nature, plants and shrubs of one kind do not 
often grow in large numbers or on large areas crowded 
together by themselves. Insects are therefore com- 
pelled to seek their food and the difficulty of finding it 
makes a very important check. The farmer removes 
that when he plants orchards and fields many acres 
in extent and puts on the same or similar crops year 
after year. Clean culture, important as it is in some 
directions, destroys the shelter of ground beetles, of 
snakes, toads, lizards, tortoises and similar creatures 
that feed on species that go underground to pupate, 
like the plum curculio, or hide just below the surface 
during the day, like the cut- worms. The war on small 
rodents is especially favorable to insects, because shrews 
and mice are great devourers of such things. Culti- 
vated areas are not sought by birds if they can find 
other quarters, and some species will simply not go 
into such places at all, even if they are never disturbed. 



252 INSECTS 

Hiding places for parasites are also limited and that is 
a matter of great moment, for some species seem to be 
dormant or in hiding for very long periods. Alto- 
gether, it may be said that in all that he does on the 
farm and in the orchard, the farmer and fruit-grower 
favors those species that feed upon his cultivated 
crops, and turns the natural scale against their enemies. 
That he does not suffer more, is merely an indication 
that these bird and animal friends that he eliminates, 
and even the predatory beetles, are not the most im- 
portant checks of the injurious forms. 

Another way in which man interferes with the 
orderly course of nature is in the introduction of plants 
from other countries, well adapted to live in the new 
locality but unable to resist the insects native to that 
place, and so giving them an undue advantage. But 
this is not a circumstance to the mischief done when 
an adaptable insect is introduced into a new country 
where it is unknown to the parasites and predatory 
forms native to that country! The wine-growing dis- 
tricts of Europe imported from America some of our 
vigorous American stocks and with them the Phylloxera 
as well. Now the Phylloxera in its native home is not a 
serious pest and there was no reason to believe that it 
would or could ever become such. But the European 
vines proved absolutely non-resistant and succumbed 
to injuries where the American vines would have shown 
no sign. The attempt to control this insect in Europe 
has cost millions of dollars and it is still an annual 
charge of many thousands on the various governments 
and growers. The difference between the American 
and European stocks is merely a matter of adaptation, 
our native varieties having become used to the insect 
when present in normal abundance. There is no specific 
native enemy to the Phylloxera and conditions in Euro- 



RELATION TO THE FARMER 



253 



pean countries are not unduly favorable to its rapid 
multiplication. Their vines are simply not used to the 
attack and sink under it. 

So on the other hand, we have a long list of insects 
in North America introduced from foreign lands. The 
Hessian fly, the cabbage butterfly, the asparagus beetles, 
the elm-leaf beetle, the cottony cushion scale, the black 
scale and the San Jose scale, are only a few of the 
well-known pests that have been with us for some time. 




Most of our troublesome forms have come to us across 
the Atlantic: the cottony cushion, black and San Jose 
scales came to us across the Pacific. The former never 
got away from the western coast ; the latter has covered 
the entire country and has become the most generally 
troublesome pest of the horticultural industry. The 
cottony cushion scale w^as eliminated by a brilliantly 
successful experiment, resulting in the inti-oduction of 
the specific check to the species from its native home. 
It was an experiment that we can duplicate at any time 
with the same factors. It is quite a different matter to 
import parasites and predatory forms hap-hazard to 



254 INSECTS 

control or affect insects with which the imported species 
is not famiHar in its native home. Here we are not 
making use of an adaptation, but are rather attempting 
to create one. Such experiments may be crowned with 
success, but it will be a success which cannot be pre- 
dicted and it will depend on factors not apprehended 
by the experimenter. 

While we have, undoubtedly, introduced into our 
country numerous first class pests — the brown-tail and 
gypsy moths among the latest — it is equally true that 
dozens of species have been introduced on imported 
stock or in other ways, that have never secured a foot- 
hold; and we have a few species that have started out 
as if to sweep all things before them and have gradually 
died out so as to become almost extinct. Two such 
species have been enemies to pear trees — the pear midge 
and the sinuate pear borer; the latter of which never 
got much beyond New Jersey, after destroying nearly 
all the pear trees in one district. One species, the 
"horn-fly," created enormous alarm among owners of 
cattle for a few years, swept over a large part of the 
United States and Canada in less than a dozen years, 
and is now so rare where it first appeared that speci- 
mens are at a premium for collectors. In none of these 
cases are specific natural enemies to be credited with 
the disappearance of the species. Conditions simply 
were not suitable in all respects, and the insects failed 
to adapt themselves Avith sufficient completeness to 
survive in the long run. 

The important point is that those species that do 
survive the introduction are exceptional in vitality and 
adaptability, and are therefore naturally abundant and 
able to maintain a lead over all their enemies. If the 
specific parasite or other check of such a form does not 
exist in the new country, and is not introduced with it, 



RELATION TO THE FARMER 



255 



a destructive increase under cultural conditions is almost 
inevitable. 

Now in what ways do insects injure the crops 
and cause injury to the agriculturist? This might 
be answered by a reference to Chapter III, but it 
may be useful to take up some features more in detail, 
with the injury rather than the insects as the prime 
objects of consideration. 

Plant lice do their mis- 
chief in part by directly 
exhausting the plant of 
sap, partly by causing dis- 
tortions of growth, and 
partly by preventing the 
proper maturing of the 
fruit, be it on shrub, tree 
or vine. If on the roots, 
the plants are weakened 
or often killed and even 
trees are sometimes seri- 
ously injured. A secondary 
cause of injury is due to 

the production of honey-dew by the lice. This serves as 
a culture medium for a black soot fungus which often 
disfigures tree fruit to such an extent as to make it un- 
salable. Some of the scales have a similar habit and so 
do some Psyllids and Membracids. The enormous re- 
productive powers of plant lice render them especially 
dangerous, and very often the farmer does not even 
see the nucleus from which come the hordes that he 
finds on his wheat, his cabbages or his melons, a few 
days later. 

During a spell of dry weather it may be noticed 
that the oats or the grass is showing white spots or 
becoming silver-tipped; or the onions begin to show 




Thrips, with antenna and 
tarsus. 



256 INSECTS 

yellow spots, turning white later, and often killing the 
tops. This the experienced grower will recognize as 
the work of Thrips, which scrape the surface so as to 
break the leaf-cells and exhaust the sap, leaving a dead 
spot. When these dead spots become sufficiently 
numerous, the leaf fails to fulfil its function and dies, or 
is only a burden to the plant. 

Leaf- and tree-hoppers do similar work and a com- 
mon example is found in the vineyard, where leaves 
often turn brown in summer before the fruit is ripe, 
because of the injuries done by the grape leaf-hopper. 

Scales, soft and armored, attack trees of all kinds, 
in the orchards, in the forests and on the city streets. 
Sometimes they are so small and inconspicuous that it 
requires close scrutiny to find an isolated individual; 
sometimes they are large and showy, flaunting their 
numbers and threats as far as the tree itself is clearly 
visible. The honey-dew and soot fungus produced by 
the soft scales have been already referred to. Many of 
the armored scales produce a specific effect on the tree, 
besides exhausting its juices. In some cases distinct 
pits or depressions are formed on the surface of the bark ; 
in others the bast is discolored and poisoned where the 
puncture is made, and when the punctures are suffi- 
ciently numerous the bast simply fails to do its work. 
Peach trees infested by the San Jose scale sometimes 
reach such a condition in fall that, after growth is 
completed, the bast has lost all vitality. During the 
winter the poison does its work; in spring the tree 
starts from the supply stored in the buds, blossoms 
and even begins to leaf out, but when demand is then 
made upon the roots for fresh nourishment the bast 
fails and the tree dies. 

This poisoning effect is not peculiar to scales, but 
is a feature in many other of the Hemiptera. Some of 



RELATION TO THE FARMER 



257 



the plant bugs of the Capsid series have it very strongly 
developed and Coreids like the common squash bugs 
are well known for the poisonous effects of their punct- 
ures on vines and other plants. 

Some plant lice form galls, sores or cankers on 
branches, trunk or even the roots, like the woolly louse 
of the apple; and some of these canker sores ofifer 
excellent points of entrance for germs of disease and 
decay. Indeed it has been charged against some of the 
species that certain plant diseases are either carried or 




Fig. 1 18. — Woolly apple- louse at c. showing galls made on roots at a, 
the woolly wingless form at b. 



given points of entrance by them. The root-feeding 
forms arc particularly dangerous, because until the 
tree or other plant begins to show bad condition there 
is no way of recognizing their presence. 

Not all the injury done by these various forms of 
sucking bugs is obvious, and so used does the farmer 
become to the loss that very often he does not appre- 
ciate it. A simple experiment made by one of our 
economic entomologists proved that leaf-hoppers in 
grass fields in his state were so numerous that they 
shortened the crop one-half. Demonstration of this 
was made by dividing a meadow into two equal parts, 
pasturing cattle on both, but collecting the leaf -hoppers 
17 



258 INSECTS 

by means of hopper-dozers on one part only. This part 
supported exactly twice the number of cattle during 
the season that could be maintained where the hoppers 
were left undisturbed. 

It is comparatively easy for the farmer to estimate 
his loss when the green-fly drains his wheat so that 
instead of the expected twenty bushels he harvests 
only ten or none at all. The drain upon all sorts of 
crops by the myriad of specimens constantly sucking 
plant juices and reducing the yield to a less obvious 
extent, is rarely capable of estimation, but varies from 
ten to fifty per cent, almost every year on most of our 
staple crops. This sounds like an exaggeration, but 
every person who has ever studied the problem at all 
carefully will agree in the estimate, I think. 

And then come the host of species that feed directly 
upon leaf tissue. They come from many orders: grass- 
hoppers, locusts, crickets and their allies of many 
kinds; slugs and grubs as well as adult beetles in great 
variety; caterpillars of the most diverse appearance 
but always great devourers; saw-fly larvae from the 
Hymenoptera and a few maggots from the Diptera or 
fly tribe. Perhaps no kinds of insects do more obvious 
injury than those that feed openly on the foliage and 
yet the real harm that they cause is not always in 
proportion to their feeding, because many plants and 
trees will support the destruction of a great percentage 
of leafage without material impairment of crops. This 
does not apply where the crop consists of the leaves 
themselves as in cabbage, spinach and other vege- 
tables, all of which have their own particular insect 
friends. 

Unfortunately some of these foliage feeders modify 
their habits somewhat, on occasion, and attack more 
important parts of the plant, e.g., when the rose-chafer 



RELATION TO THE FARMER 



259 



eats by preference the flowers of the grape and thus at 
once destroys the crop without injurmg the plant 
itself. Some cut-worms, hiding out of sight during 
the day, cut off the stalk at base for convenience of 
feeding, leaving the tops on the surface to dry and 
perish. Or they climb on the shrub or tree and eat 
out the buds or growing tips, destroying the crop if 
not the plant. 

This brings up the fact that in his method of culti- 
vation the farmer frequently forces upon himself an 
injury which the insects would not under normal con- 
ditions inflict. If a field be left fallow or in grass for a 
year or two, it will almost inevitably attract the night- 
flying or owlet moths of the family NoctnidcB, whose 
larvae, the cut-worms, feed normally on grasses and a 
great variety of low plants. These cut-worms, or many 
of them, winter half grown in sod or rubbish on the 
surface of the ground, coming out to resume their 
feeding in spring. If now, in early spring, the farmer 
plows this infested sod and plants com or potatoes, 
or sets out cabbages, tomatoes or sweet potatoes, he 
deprives the cut-worms of their natural food and prac- 
tically forces them to take what he has set in its place. 
Furthermore, while a popidation of one cut- worm per 
square foot would not be a very serious infestation in 
grass land, it would be destructive in a cornfield, or in 
a cabbage patch. And not only are cut-worms favored 
in this w^ay: there are weevils known as bill-bugs, 
attacking corn planted on timothy sod or following 
certain other grasses, and there are wire-worms and 
white grubs that attack cultivated crops when they are 
put in after grass or other infested plants. Of course 
this means bad farm practice from the standpoint of 
the entomologist; but not until quite recently have the 
farmers been willing to consider any modification 



26o 



INSECTS 



merely because it would produce conditions less favor- 
able to insect increase. 

Besides those species devouring foliage above ground, 
there is a large subterranean population of wire-worms, 
white grubs, maggots, slugs, and the like that attacks 





Fig. 119. — A bill-bug, its larva and work in root of Scirpus. 



the roots of plants. The underground work of plant 
lice has been already mentioned; the species now 
referred to are those that actually devour the root 
tissue or dig into the underground stem so as to destroy 
or weaken the overground plant. Cabbage, onion, 
radish and other root maggots, wire- worms, grub- 
worms, grape-root worms, root-borers — all arc familiar 



RELATION TO THE FARMER 261 

terms to the farmer, and represent sources of injury 
that he has learned to dread. 

And when his plants have developed well, his fruits 
have set and all looks fair and free from any of the 
pests already enumerated, the farmer is by no means 
certain that he will get either seed or fruit. There are 
numerous midges that develop in the ovaries of fruits 
and flowers, and either feed directly in the seed or 
suck its juices so as to shrivel it. We have species that 
attack the kernels of wheat, rye, oats, sorghum and 
other grains; others that get into the ovaries of the 
clover flower and destroy the seed — so thoroughly, 
indeed, that in some localities, while it is easy to get 
good crops of clover hay, it is impossible to get any 
seed at all. Midge larvse, indeed, are found under the 
most divergent conditions and their injuries are by no 
means appreciated as yet to their full extent. Not 
that the midges are alone in this work, for among the 
beetles there are a large number that infest special 
crops. There are, for instance, the BnichidcB, contain- 
ing the bean and pea weevils that infest seeds of all 
sorts of legumes, from the pods of the locust tree to 
those of the lentil. Sometimes only a single larva 
develops in a seed as is the rule in peas, or there may be 
up to half a dozen or more in a single bean. And the 
worst of it is not the infestation that comes in the 
field alone, but the likelihood that without great care 
it may be brought and continued in the bam or store- 
house. Even after harvest the wheat is not safe, for 
if it be left in shocks in the field, the Angoumois grain 
moth is apt to find it and start its work of destruction. 

Further, among the snout beetles we have species 
that confine their attacks to the buds or developing 
seed capsules. The boll-weevil of the cotton is perhaps 
the most conspicuous example, and this species alone 



262 INSECTS 

has demanded the expenditure of hundreds of thousands 
of dollars in its study and attempted control, and has 
injured the value of the crops in the affected states by 
many times that amount. Less conspicuous but equally 
destructive on a smaller area is the strawberry weevil, 
which develops in the bud, preventing the formation 
of fruit. 

This habit of placing the eggs in a protected position 
or with reference to the food supply of the larva is 
quite a trick among the snout beetles, and some of their 
habits are very interesting as well as economically 
important. The nut-weevils have the snouts very 
much elongated and very slender so that they are 
enabled to pierce the growing burr or husk and place 
the egg in the developing nut, long before there is a 
shell to be reckoned with. The plum curculio cuts a 
little flap from the surface of the fruits that it infests 
and in this bit of loosened tissue lays its egg, safe from 
the pressure that might otherwise be exerted upon it 
by the growing fruit. And so it is with other of the 
Rhynchophora that attack our fuits, large and small. 

Even tree fruits are not exempt from midge attack, 
one form depositing its eggs in the pear bud that the 
young larvae may be in position to get down into the 
seed capsule while yet the passage-way into the ovary 
is wide open. Other files attack growing fruits of many 
descriptions and are furnished with a horny ovipositor 
of considerable length for puncturing the skin. Apple, 
orange, olive and plum, all have their "fruit-flies" that 
demand toll of varying importance. 

Among the Lepidoptera, none is better known than 
the codling moth, the larva of which feeds in apple, 
pear and quince. Where no active measures are taken 
for its control, it is no unusual matter to find from 90 
per cent, to 95 per cent, of all the fruit on a tree wormy 



RELATION TO THE FARMER 



263 



and of inferior value. This species seems to be dis- 
tributed wherever the apple is grown. Other species 
attack grapes in a similar manner and there are feeders 
among the smaller caterpillars in or on almost every 
fruit that grows. Besides feeding on or in the fruits, 
many of them are also miners in leaves and even in 
twigs and branches. There is, of course, a great deal of 




Fig. 120. — Codling moth and its work: a, the injury done; b, place where 
egg was laid; c, larva; d, pupa; i, cocoon; /, g, adults. 



difference between the amount of injury caused and 
usually a species is confined to either one kind of plant 
or to the members of one plant family. There are a 
few, however, that are obnoxious to a variety of crops 
and none that occurs to me at present is much worse 
than the corn-worm, boll-worm or tomato-worm, as it 
is variously named. It winters, usually in the pupal 
stage, underground, and early in the season emerges as a 
yellowish, inconspicuous owlet moth, which during the 
month of May in the middle states seeks a place to lay 



264 



INSECTS 



its eggs. At this time the most attractive things seem 
to be the early peas, and very soon the greenish cater- 
pillars will be found boring into the forming pods. 
As the young com makes its appearance this becomes 
attractive to the moths of the second brood, and the 
caterpillars, now usually with a pale reddish-gray tinge. 




-Heliothis armiger: a, b, CRgs; c. larva, ("corn- worm", 
■m", and " tomato- worm ") ; d, pupa in cell; e. f, moths. 



•boll- 



appear as stalk-borers. As the sweet corn advances the 
caterpillars find the forming ears, and many a barren 
stalk is so because the ear has been eaten even before 
it appeared between the leaves. About this time, too, 
the earliest tomatoes become of nice size and offer 
another outlet for the caterpillars, which bore into the 
fruits when they are nearly ready to color and take 
those specimens which would otherwise have sold for 
fancy prices. In the southern states the cotton at this 



RELATION TO THE FARMER 265 

time begins to offer an attraction in the shape of form- 
ing buds, and a Httle later the "boll- worm" makes its 
appearance. When com is plenty, that forms an at- 
traction superior to everything else and then come the 
"corn-worms" so common and objectionable in the 
"roasting ears." Sometimes there is only one, usually 
of good size; sometimes there are several, usually 
smaller, and the explanation is that the insects are very 
pugnacious and when they meet they fight. When 
there are two or more full grown larvae in one ear, it 
simply means that they have never chanced to meet. 
The caterpillars continue in the com until it is cut and 
stacked, and some may yet be found at husking time; 
but from the time the kernels begin to harden they go 
underground as they mature and change to that pupal 
stage in which they safely pass the winter. After they 
once get started in spring they can be found almost 
continuously in some one or the other of their food 
plants. 

There remains yet one more way in which growing 
crops are attacked and that is by borers, and these 
also are of many kinds and all sizes. The stalk of wheat 
and the fruit tree fifty years old are equally subject to 
this kind of injury, and larvae of Coleoptera, Lepidoptera^ 
Hymenoptera and Diptera all contribute to the mischief. 

Some of these stem feeders really do not deserve 
the name of borers at all, as for instance the larva of the 
Hessian fly, which attacks wheat stalks at the base and 
produces a gall that checks growth, or the joint-worm 
which works into the stem at a joint; but for conven- 
ience we may class as borers all forms which feed out 
of sight in stems, twigs, branches or trunks. And it is 
astonishing what a variety of borers there are and how 
generally plants are infested. Not cultivated plants 
only, but arrant weeds like burdock, thistle, rag- weed 



266 INSECTS 

and the like. We find among Dipterous larvae maggots 
in some variety, often producing swellings oi* galls in 
herbaceous stems, besides the numerous midge larvae 
already so often mentioned. Hymenopterous borers 
are comparatively few in number and chiefly members 
of the saw-fly or horn-tail divisions. Some of these are 
in grasses including grains, and are slender, white, 
caterpillar-like forms which often hollow out the entire 
length of a stalk. Pithy stems like those of blackberry 
and raspberry are favorites with this kind of borers, 
not many of which belong to the seriously injurious 
class. The horn-tails attack woody plants more gen- 
erally, but are also comparatively few in number, both 
as to species and specimens. 

Lepidopterous or caterpillar borers we have in great 
variety and in all kinds of plants and trees. The largest 
of them belong to the Cossids and Hepialids, the giants 
among the so-called Microlepidoptera. Most of these 
are confined to forest trees, and it is notable that our 
only really troublesome species is an imported one — 
the wood-leopard moth — that attacks shade and orchard 
trees. In this connection it is interesting to observe 
that the boring habit among Lepidoptera is an ancient 
one, not even confined to terrestrial vegetation, and 
that by far the greatest number of the borers of the 
present day are members of the simpler and earlier 
types of Microlepidoptera. 

Wood-feeders largely we find in the Sesiid clear- 
wing moths, among which are some of our most trouble- 
some species, e.g., the peach borer, cherry borer, cur- 
rant borer, blackberry borer and the like. Some live 
in the solid wood of trunks and bra.nches, like the cherry 
borer and those that live in oak, maple and other trees: 
some live just beneath the bark and make chambers 
rather than galleries, like, the peach borers: others are 



RELATION TO THE FARMER 267 

in roots like the blackberry crown borer and the grape 
root borer; while yet others feed in the centre of a 
stem, like the currant borer or lilac borer. Among the 
Pyralid moths there are numerous borers in herbaceous 
plants and among the Noctuid or owlet moths there is 
quite a series in which the boring habit is well devel- 
oped; such plants as potatoes, tomatoes, com and 
wheat being among the victims. A few are twig borers 
on trees, like those working in the terminal shoots of 
peach and plum. 

It is among the Coleoptera or beetles that boring 
habits are especially well developed. There is almost 
no sort of tree or plant among our cultivated species 
that is not more or less infested by coleopterous borers 
of some kind, and in a very general way that same 
assertion might be made of all trees and plants. So 
general is this habit that except in the predatory and 
scavenger forms, there is scarcely a series that does not 
have some sort of boring species included in one or 
more of its families. The Longicoms and Buprestids 
are almost all borers in woody tissue; among the 
Rhynchophora or snout beetles there are numerous 
borers in herbaceous plants and a goodly representation 
that works in woody tissue. Apple, pear, quince, peach, 
plum, nut and citrus trees are all more or less subject 
to attack, and grape, blackberry and other vine and 
small fruits are equally apt to be infested. Potatoes 
have weevil borers in the stem, many grasses have 
similar borers in the roots, and even cabbage has its 
leaves and stem more or less riddled. Among the 
tree borers there are two rather well-marked types 
represented by the round-headed and fiat-headed bor- 
ers. The former quite usually do most of their work 
in solid tissue, the latter are more apt to make channels 
in the bast or between bark and sap-wood, getting into 



268 INSECTS 

the solid wood only to pupate. Some of the round- 
headed borers have similar habits but on the whole 
they are more diverse in their methods of feeding than 
the flat-headed borers. With both we have species 
that attack only dead or dying tissue, and others that 
will feed in or on perfectly healthy trees. Some of them 
must have matters just exactly right, like the twig- 
girdler which lays an egg and then girdles the twig 
below the point of oviposition, so that in the first high 
wind it may break off and fall to the ground. Others 
like the oak-pruner demand living wood as food for 
the larva, but a dead twig for pupation; so the larva 
girdles the twig from the inside, leaving only a thin 
shell, makes itself comfortable beyond this point, and 
waits the time when it is blown to the ground to com- 
plete its transformations. 

Another important series contains the bark beetles 
which, while they do not so much affect the horticul- 
turist, do most seriously affect the forester and the 
lumberman. It would hardly pay to go at much 
greater length into the different kinds of borers, be- 
cause the fact of general infestation has been suffi- 
ciently brought out. 

We see from this brief review that from the time the 
plants first show above ground until the harvest is in, 
they are subject to the attacks of sucking and chewing 
insects in all their parts, and that neither root, stem, 
leaf, fruit nor seed is free from liability to infestation 
and injury. Some of this liability is increased by inju- 
dicious farm practice, some of it is the consequence of 
past carelessness, and a portion is due to the inevitable 
change in the balance of nature caused by culture and 
by planting large areas in one sort of vegetation. 

It follows that the agriculturist and horticulturist 
is always at war with insects, either actively or pas- 



RELATION TO THE FARMER 269 

sively, and he always suffers some injury, large or 
small in proportion to the activity of his campaign 
against them. "What is not always realized by the 
passive resistant is that what he loses is all profit. 
It costs about so nnich to prepare, plant and harvest 
an acre of corn, wheat, potatoes, cabbage or other 
crop, and if the insects eat 10 per cent, of what W'Ould 
have been produced had they been destroyed, that 10 
per cent, is directly out of the farmer's pocket. And 
if in two orchards of the same variety, producing exactly 
the same number of barrels of apples, those from the 
one are clean as the result of an active campaign and 
the latter gnarled and wormy from curculio and codhng 
moth, the difference in price between the fancy fruit 
selling at the top of the market, and the other fit only 
for the cider mill, is the measure of loss, since the cost of 
handling and growing is practically identical. 

It has been attempted again and again to calculate 
and estimate the annual loss of agricultural products 
due to insect ravages in the United States and Canada, 
and no one has fixed it in figures of less than hundreds 
of millions. As a matter of fact, the money loss is 
difficult of estimation, because any material addition to 
the amount of a crop might have a decided influence 
on its price. It is not uncommon, for instance, for a 
farmer to make more money on a short crop than out 
of an excessive one, and this factor has been previously 
noted by Dr. L. 0. Howard, in his discussion of the 
same subject. A better basis, perhaps, is the percent- 
age of crop destroyed, and that has been estimated at 
anywhere from 10 per cent, to 25 per cent, of the total. 
The careful student will be inclined to consider the 10 
per cent, estimate too low; it is doubtful whether, in 
actual lessening of crop, it will reach the 25 per cent, 
mark; but if we take into consideration the lessened 



270 INSECTS 

value of much of the crop actually harvested and 
marketed, I believe that 20 per cent, depreciation in 
value of farm products is not too high an estimate of 
the losses annually caused by insects in the United 
States and Canada. As the value of such products 
was estimated in the Report of the U. S. Department of 
Agriculture for 1907 at $7,412,000,000, the estimated 
loss, due to insect ravages in the United States alone 
should be put at $1,500,000,000 at least. 



CHAPTER XII 

THE WAR ON INSECTS 

Having detailed the character of the injury done 
by insects and given some idea of its extent, the question 
arises; what can we do to prevent such loss, and what 
has been done in this direction? There is yet, in the 
older settled portions of our country a rather widely 
distributed feeling that as insects exist and feed on 
plants, they were created for that purpose and that it 
is meddling with a divine institution to attempt their 
destruction or limit the amount of injury done. It is 
the same sort of spirit that protests that "it can't be 
done" whenever any attempt is made to better sani- 
tary conditions, to control the spread of disease or to 
limit the agencies that make for the spread of infection. 
Supplemented by the equally wide-spread conviction 
that any grown man that engaged in so trifling an 
occupation as the collection and study of insects must 
of necessity be deficient in intellect or of unsound 
mind, this condition was responsible for retarding the 
development of economic entomology to the middle of 
the last century, and even then it developed slowly 
and failed of general appreciation. 

With the establishment of agricultural experiment 
stations under the Hatch Act of 1887 conditions began 
to change. Entomologists were appointed in several of 
them; their work began to make itself felt, its im- 
portance began to be appreciated, and now there is 
scarcely a state or territory in which there is not at 
least one working economic entomologist. In 1889 an 
Association of Economic Entomologists was formed 
271 



272 INSECTS 

with about a dozen members. In 1907 there were 
enrolled among the active and associated members, 
most of them in official positions, no less than 211 
names; and that does not include all of them. Of 
foreign associates interested in the same line of work 
there are forty-five, and that includes most of those in 
official positions. In 1888 there were less than half a 
dozen makers of pumps or machinery suitable for 
insecticide work, while nozzles were difficult to obtain 
and poor. At present there are numerous makers of 
machinery and each of them presents a long line of 
pumps, nozzles and fittings for applying insecticides 
and fungicides. On the Pacific Coast the problems 
were somewhat different from those of the Atlantic 
Coast and the line of development in the production of 
insecticides and spraying machinery was also different. 
Fumigation with hydrocyanic acid gas, the lime and 
sulphur and resin-washes are Pacific Coast contribu- 
tions; the development of the arsenical sprays and the 
mineral oil preparations are to be credited to the Atlan- 
tic Coast, or at least to the territory east of the Rocky 
Mountains, for much of the pioneer work with insecti- 
cides was done in Illinois and Missouri, by Walsh 
and Riley. 

In 1889, every ounce of kerosene emulsion was 
home-made, and Paris green, London purple, helle- 
bore, tobacco and pyrethrum were practically the only 
insecticides on the market. There was whale oil soap 
also, but expensive and an unknown quantity as to 
its ingredients. Now there are a large number of 
manufacturers throughout the country, producing com- 
mercially every preparation that has proved useful in 
the hands of experimenters, and chemists everywhere 
are seeking to improve and cheapen the known combi- 
nations or to devise new and more effective ones. Mis- 



THE WAR ON INSECTS 273 

ciblc oils and lime and sulphur combinations are made 
and shipped in car-load lots, while arsenate of lead, 
absolutely unknown as an insecticide in 1888, is sold in 
ton lots to individual purchasers. 

This development in the face of at least passive 
opposition could not have taken place in so short a 
time as twenty years had it not been promptly dem- 
onstrated that the fight was a paying one. And when 
the reader who remembers the fruit markets of that 
earlier period, compares them with the magnificent 
productions in our markets at present, he will realize 
the advance that has been made. Farming and fruit 
growing has been developed as a science, along scien- 
tific lines. The soil is a chemical laboratory, with 
elements ready to be combined into organic compounds 
under proper conditions. The plants produced in this 
soil and from these elements serve naturally as food 
for man and other animals, including insects. Man 
wishes to get it all for his own use and, of course, 
therefore desires to eliminate the insects as partners. 
Can he do it, and if so, how? 

To the first part of the question we answer yes, to a 
very great extent; to the second there is a less definite 
answer since every group of species must be dealt with 
according to its kind and no one application will serve 
for all kinds of species. Often, indeed, where insecti- 
cides cannot be used at all, we can circumvent by plant- 
ing at proper times, rotating crops so as to prevent 
undue increase, and by harvesting so as to destroy the 
insects before they mature. In the garden and in the 
greenhouse where conditions are more under our 
control, injury from insects can be reduced to a mini- 
mum, and the records from our orchards show that 
wormy fruits are not necessary features in a crop. 

We have learned that as against practically all 



274 INSECTS 

insects that chew their food and feed openly upon 
plant tissues, arsenical preparations may be used with 
good effect. Up to within a few years Paris green was 
practically the only satisfactory material of that char- 
acter, and even that could not be used on tender foliage 
or on conifers without extreme caution. Recently, the 
manufacture of arsenate of lead has been developed to 
a point that we have now a satisfactory killing agent 
that can be safely used at any strength on foliage of 
any kind. It has the further advantages of remaining 
well in suspension without constant stirring, and of 
sticking to the foliage indefinitely after it has once 
dried. In the garden and greenhouse no other stomach 
poison should be used and it will be found effective 
against all caterpillars, saw-fly slugs, beetles and their 
larvae and generally against insects that actually eat 
foliage; it is useless against sucking insects such as 
plant lice, scales, plant bugs and the like. It contains 
less actual arsenic than Paris green and at least three 
times as much must be used to obtain the same results. 
One pound in lo gallons of water will kill potato beetles 
and their larvae; i pound in 50 gallons of water will 
kill slugs and small caterpillars; i pound in 25 gallons 
of water is a good general strength for ordinary cater- 
pillars and other similar species. Paris green is perhaps 
a little more economical in orchard work and can be 
used at the rate of i pound in 50 gallons of water for 
potato beetles, i pound in 125 gallons for orchard work 
and I pound in 150 gallons on sensitive foKage or against 
young caterpillars. It should never be used on peach or 
conifers and should be very cautiously used in the 
garden. It is well to slack one pound of quick-lime 
with every pound of Paris green to combine all the 
water-soluble arsenic in the insecticide, especially when 
used at the greater strengths. 



THE WAR ON INSECTS 



275 



Arsenate of lead comes in paste form only, at present 
writing, and cannot be applied dry.* Paris green can be 
mixed with air-slacked lime or dry hydrate and applied 
with a bellows, and for cases where a powdery dusting 
will form as satisfactory a coating as a spray, the appli- 
cation in that manner is just as good. There are cases, 
however, as where an insect feeds only on the under- 
side of a leaf, where a dust does not and cannot cover as 
well as a spray, and others where the material must be 
forcefully applied so as to get into a crevice or cavity 
in order to secure a maximum effect. 

There are preparations of white arsenic which can be 
made at home, forming combinations with lime which 
are stronger and cheaper than either Paris green or 
arsenate of lead; but these are dangerous in unskilled 
hands and require so much care in preparation that 
they are not advised, save when very large quantities 
of material are needed. 

It is very often desirable to combine an insecticide 
and a fungicide so as to prevent injury from disease as 
well as insects, and Bordeaux mixture is the fungicide 
generally used with either Paris green or arsenate of 
lead. This Bordeaux mixture is in itself very offensive 
to many insects and some of the flea beetles will scarcely 
touch a plant protected by it. If the arsenical insecti- 
cide is added to the fungicide in the same proportion 
as if it were water, an extremely effective material is 
obtained. The Bordeaux mixture is prepared as follows: 

Copper sulphate 4 pounds 

Quick-lime, stone or shell, good quality .... 4 pounds 
Water 50 gallons 

Dissolve the copper sulphate in one gallon of hot 
water, slack the lime in water sufficient to do it well, 
and strain. These are the stock mixtures and will 

* A dry powder has been produced, but is still in the experimental stage. 



276 INSECTS 

keep a long time if tightly covered. To prepare for use 
dilute each of the stock mixtures with ten gallons of 
water, combine them in a barrel of sufficient size, and 
then add water to make up the full amount. Never 
combine the concentrated stock mixtures as it pro- 
duces a heavy coarse precipitate that is much less 
efifective. The above mixture is the full strength that 
is reasonably safe for general use. The tendency is to 
use only three pounds of copper instead of four on 
orchard trees, and on peach it should be even weaker, 
if used at all. 

Against plant lice, scale insects and other sucking 
insects our battery is much larger, much less satisfac- 
tory, and applications must be much more carefully 
made. We can spray a tree with arsenate of lead to 
reach an insect which we expect will make its appear- 
ance to-morrow; but a contact insecticide must be 
applied when the insects are actually present and must 
be brought into actual touch with the specimen before 
it can be effective. 

Contact poisons kill either by direct corrosive action 
on the skin of the insect, as where dry hydrate of lime 
is dusted on a soft slug, or by clogging or entering the 
body through the spiracles or breathing pores. Soap 
mixtures clog by forming a film over the openings and 
matting up the hairy guards that as a rule protect 
them; a soap that makes a rather thick slimy suds is 
therefore preferable to one that forms a clean, thin 
suds. Mineral oils are very penetrating and kill by 
getting into the body cavity through all openings. 
Decoctions like those of tobacco and hellebore get into 
the spiracles and perhaps also through the mouth into 
the stomach and set up a convulsive affection that re- 
sults in death. Dry powders like hellebore and tobacco 
are effective in proportion as they are finely ground, and 



THE WAR ON INSECTS 277 

even fine road dust has some insecticide value. The 
fine dust particles get into the trachea and there set up 
specific irritation, but they must get there to do any 
good at all. Coarse particles are no better than so 
much coarse dust and insects with covered spiracles are 
not affected at all. It is quite possible, therefore, to 
have an insecticide which is very effective against one 
series of a species, but which, against another series, 
will be entirely useless: any material for which it is 
claimed that it will kill everything, should for this 
reason be looked upon with distrust from the start. 

Plant lice are among the most common of all the 
insects to be dealt with in a practical way, because 
there is almost no vegetation not more or less infested 
by them. In a small way on house plants, insect powder, 
i.e., pyrethrum, is the cleanest and simplest remedy. 
It can be dusted on through a sieve, put on with a little 
powder puff or bellows, or it can be made into a decoc- 
tion or tea, using an ounce to two quarts of hot water. 
This can be put on with an atomizer and, when fresh, it 
is very effective against all kinds of plant lice, against 
most small caterpillars and slugs, and against the 
larvce of scale insects. It loses strength rapidly when 
exposed to the air, and in corked bottles the decoction 
ferments and moulds after a day or two. It is alto- 
gether too expensive for general use in fields, but in 
gardens or greenhouses its cleanliness and absolute 
safety to plants are in its favor. 

Tobacco has a much greater range of usefulness. 
When very finely powdered it ma}^ be dusted on and 
will kill about the same sorts of insects as the pyre- 
thrum. It may be worked into the soil of pots and 
benches to kill root lice, besides discouraging many 
other underground insects. It is also a fertilizer and 
stimulates the plants to which it is applied. If a spray 



278 INSECTS 

is preferred, one pound of chopped tobacco stems may 
be boiled in one gallon of water until a dark brown 
extract is obtained, and this will control white fly, 
mealy bugs and most of the other greenhouse pests, 
provided it be frequently and thoroughly applied. It 
stains delicate flowers and is apt to cause a little injury 
to very delicate foliage, but in general it is safe on all 
ordinary plants. The cost of tobacco dust or ground 
tobacco is low enough to warrant its use in gardens 
and fields, and we have no better remedy for root lice 
on trees and plants; even the woolly apple louse suc- 
cumbs to a liberal application. To reach such insects, 
the soil must be removed to a depth of at least six 
inches in a circle from eighteen to twenty -four inches 
around the trunk, varying according to the size of the 
tree, before a layer of ground tobacco is put on, and the 
trench must be then filled up. The soil moisture and 
rains extract the nicotine and bring it into contact 
with the root lice. Stems, whole or coarsely chopped, 
are of very little use, since the nicotine is extracted so 
slowly as to be ineffective. Tobacco is also used in 
greenhouses as a fumigant and is quite effective against 
a great variety of pests. It may be burnt on a layer of 
hot coal in an open stove, an extract may be smeared 
on the pipes for slow evaporation, or paper-rolls soaked 
in the extract may be burnt on wires suspended in 
different parts of the house. And that brings up the 
point that there are now on the market commercial 
extracts under various names which, when only small 
quantities are to be used, are cheaper and better than 
can be made at home. They must, however, as a rule 
be used at greater strength than recommended on the 
labels in order to be thoroughly effective. 

Soaps are also used against plant lice and other 
sucking insects and these have a much greater range of 



THE WAR ON INSECTS 279 

effectiveness than the extracts just mentioned because 
of their greater penetrating power. All soaps have 
some insecticide value, and so washing the leaves of 
house plants with soapsuds is always good practice 
provided the suds be not too strong. An ounce of soap 
to one quart of water is ordinarily quite sufficient to 
kill green lice and young scales, especially if whale oil 
soap is used. At tw4ce that strength it kills even the 
more resistant forms of plant lice, but becomes danger- 
ous on tender plant foliage. While soapsuds may be 
freely used on house plants, the suds should not be 
allowed to accumulate on the surface of the soil for the 
alkali may easily become detrimental to the plant roots. 
For greenhouse and garden use, whale oil soap is much 
improved by an addition of tobacco and such a combi- 
nation is now obtainable from most seedsmen. 

In the field, whale oil soap is much used against 
plant lice, and is effective at varying strengths de- 
pending on the insects to be reached. Against most 
green lice i pound to 4 or even 6 gallons of water may 
be satisfactory; against brown or black Aphids twice 
that strength may be required, and against young scales 
I pound in 2 gallons is the weakest mixture that can be 
effectively used. For winter work against armored 
scales Hke the San Jose, 2 pounds in i gallon of water 
are applied. 

In all dealings with plant lice and similar insects 
that multiply rapidly, prompt action is essential for 
best results. It is sometimes easy to destroy a slight 
infestation and to get rid of a few specimens on leaves or 
stems. If they are allowed to multiply unchecked 
until the plant begins to show signs of suffering, it will 
be necessary to make much more thorough treatments, 
and as many species tend to curl or otherwise to dis- 
tort the leaves, hiding in the shelter thus caused, it 



28o INSECTS 

becomes also more difficult to reach them. It must 
always be remembered that no contact poison can be 
effective unless it actually touches the insect aimed at, 
and covering the top of a leaf no matter how thoroughly, 
when the insects are feeding on the underside, is of 
little or no use. More ill success results from a failure 
to recognize this fact, than from any deficiency in the 
material applied. 

There are a large number of "patented" or pro- 
prietary insecticides on the market for killing plant 
lice, scales and similar insects, and some of these are 
really meritorious; but they are usually expensive and, 
in the long run, no better than the materials we have 
just enumerated. 

While it is comparatively easy to reach and control 
plant lice on most ordinary farm crops and in the 
garden, it is decidedly more difficult to reach scales 
whether soft or armored, and even mealy bugs are 
difficult to kill, in spite of the fact that they are com- 
paratively unprotected. 

There is only one period in the life of such insects 
when they are within reach of mild applications and 
that is when the young have just hatched and are 
moving about without protective covering. Theoreti- 
cally that is the best time to reach them and with some 
species it is practically the only time. The oyster 
shell scales and some others that attack our trees and 
shrubs winter in the egg stage under the mother scale, 
practically safe from all our known mixtures. Early 
in the season, depending of course on latitude as to the 
exact time, these eggs hatch, all at about the same time, 
so that for two or three days there is a great swarm of 
naked larvae, and for a week there are newly set scales 
with the thinnest sort of protective covering; that is 
the time for whale oil soap, kerosene emulsion, miscible 



THE WAR ON INSECTS 281 

oils or whatever else is depended upon to reach the 
insects. After the scale has once hardened, none of 
our summer applications that are safe on foliage can be 
relied upon to kill. A large number of scales, soft as 
well as armored, come under this general rule as to 
development and treatment, and the gardener or farmer 
who has insects of this kind to deal with, should know 
their life cycle sufficiently well to know when to make 
his applications. 

Scales that bear living young usually winter in the 
partly grown condition and may be reached by appli- 
cations which either penetrate through or under the 
protective covering to the insect beneath. When repro- 
duction begins the larvae are bom singly, a few each 
day, and this may continue for two or even three weeks. 
By the time the last young emerge, the earliest are 
already well grown and covered with scales, so there is 
no time when a single application will reach more than 
a small proportion of the infestation. If sprayings 
could be made every third day so long as reproduction 
continues, satisfactory results could be gotten; but 
while this may be feasible in the garden and green- 
house, it is not practical in the field and orchard. In 
large greenhouses this method is often resorted to and 
the scales on palms and other hot-house plants are kept 
under control by frequent application of weak material. 

In the orchard much more drastic measures must be 
resorted to, and in winter when the plants are dor- 
mant, very caustic or very penetrating materials are 
used. For caustics nothing is much better or more 
generally effective than the lime and sulphur wash, 
formed by combining one pound of ground or flowers 
of sulphur with one pound of unslacked stone or shell 
lime in three gallons of water. This combination is 
made by boiling the lime and sulphur with just enough 



282 INSECTS 

water to do it properly and afterward diluting to spra}'- 
ing strength. It usually requires about one hour's 
boiling to get the proper combination and, when re- 
duced with warm water and applied fresh on peach 
and plum trees, there is no more effective remedy 
against the pernicious or San Jose scale. The material 
is, of course, quite as efifective a killing agent on other 
trees as well; but on pear and apple it is more difficult 
to reach all the specimens in their hiding places behind 
or under bud or bark scales, in crevices or, in the case 
of apples, among the hairy clothing of the terminal 
shoots. On such trees the wash should be applied with 
great force and as thin as possible so as to aid its pene- 
tration. On peach, plum and apricot trees it exercises 
also a beneficial effect in checking certain fungus dis- 
eases and improving the general health of the tree. 
On trees in fohage this wash should never be used, nor 
on conifers of any kind. As to the practical work of 
making the wash, place the lime and the sulphur in an 
iron kettle over a brisk fire, pour in hot water enough 
to cover and start slacking, which will bring the mass to 
the boiling point at once. Add hot water slowly, stir- 
ring to prevent burning and to facilitate the combination 
of lime and sulphur. One part of good lime is a little 
more than enough to combine one part equal in weight 
of sulphur and any excess of lime remains as white- 
wash and adds nothing to the effectiveness of the 
material. If the lime is poor, a little more should be 
used to make sure that all the sulphur is combined. 
If flowers of sulphur are used, three-quarters of an 
hour's boiling is sufficient if hot water is used as a 
starter. Otherwise an hour is better. If ground sul- 
phur is used boil half an hour longer. 

Where large quantities of the wash are to be made 
up, live steam is quite generally used, and the mixture 



THE WAR ON INSECTS 283 

is made in barrels into which Hvc steam is led from a 
central boiler. These plants vary so greatly that only 
the principles upon which they are built can be stated. 
In all cases there is a drop from an elevated steam pipe, 
reaching to the bottom of the barrel, where there are 
usually cross arms of perforated iron pipe to permit 
the steam to get to all parts of the mass and prevent 
irregular cooking. The proper amounts of lime, sulphur 
and water are put into the barrel, and the steam is 
turned on for an hour or longer, until the combination 
is completed. 

It is also possible to make a good combination of 
lime and sulphur by the heat of slacking lime alone, or 
by using potash in addition to the lime to produce the 
proper degree of heat. It requires heat to combine the 
lime and stilphur and it matters little whence this heat 
comes; whether from burning wood or coal, from steam, 
or from slacking lime, soda or potash. The wash is 
effective in proportion to the completeness of the 
combination and the thoroughness of the application. 

To make the lime, soda and sulphur combination 
put into a barrel 22 pounds of best quality stone lime 
and add hot water enough to start slacking. While 
this is in progress sift in 10 pounds of flowers of sul- 
phur, stirring and adding hot water as needed until 
the mass is well reduced. Then add 11 pounds more of 
lime with more hot water, and sift in 7 pounds more of 
sulphur while tliis is slacking. Before it is done steam- 
ing, stir in i^ pounds of caustic soda which will cause a 
violent boiling, and when this begins to subside add an 
equal amount and then again another ij pounds, 
making 4^ pounds altogether. Keep stirring and 
adding hot water slowly until the combination is com- 
pleted. Then add hot water to make 50 gallons and 
apply at once. 



284 INSECTS 

To make the self-boiled lime and sulphur combina- 
tion, place forty pounds of best quality stone lime in a 
barrel, sifting in twenty pounds of sulphur flowers with 
it so that it is well mingled. Add boiling water enough 
to start a brisk slacking and cover with a heavy blanket 
to confine the heat. Add hot water as needed to keep 
up the slacking, and stir occasionally to aid the combi- 
nation. Keep this up until the lime is fully reduced and 
mixed with the sulphur. Then let the combination stand 
covered for an hour to maintain its heat, after which hot 
water enough to make fifty gallons should be added. 

The objection to these mixtures is that unless they 
are very carefully made there will be a considerable 
percentage of uncombined sulphur which is of no value, 
and there is so great an excess of lime forming white- 
wash, that it makes the wash too thick to get into 
crevices or through plant hairs. But even this wash is 
now made commercially and there are several brands 
on the market which, when thinned down for use, cost 
very little more than the home-made wash, and much 
less to the man who has no plant available for making 
up small quantities. Some of these brands have been 
tried in comparison with the home-made wash and, 
when reduced no more than nine times, they were 
quite as effective. The gardener who has only a few 
trees to be treated will save time and money by using 
the commercial preparations. 

This wash is extremely caustic and corrosive. Ma- 
chines in which it has been used should be thoroughly 
washed out and oiled before being put away, the hands 
should be protected by gloves while spraying, the face 
should have a coating of vaseline, and if there is much 
wind the eyes should be guarded by goggles. ' 

As already indicated this wash was developed on 
the Pacific coast, and it is undoubtedly more uniformly 



THE WAR ON INSECTS 285 

effective there than it is on the Atlantic coast. A 
variety of reasons for this difference have been sug- 
gested, but for our purpose it is enough to recognize 
that the fact exists. 

Sulphur by itself is not a mean insecticide if we 
stretch the term insect just a little so as to include the 
mites. In the greenhouse, against red-spider there is 
nothing much better than flowers of sulphur dusted on 
the surface, where the slow decomposition generates 
fumes that are fatal to the mites and not conducive 
to the multiplication of other parasitic organisms. 
In the citrus orchards of Florida a similar practice is 
adopted to prevent injury from the rust mite; lump or 
ground sulphur is used, and here the hot, moist 
atmosphere favors effects that are unobtainable in the 
dry climate of the Pacific Coast regions. 

A barrel half full of lump sulphur set in a warm 
comer of the greenhouse and kept filled with water is 
an excellent spraying solution for general use on the 
benches. There is very little sulphur in the solution, 
but there is enough to keep down mites, check mildew 
and destroy many other spores of disease organisms. 
As the water is used, more is added, so that half a 
barrel of sulphur may last a year or more. It needs a 
warm corner to start decomposition. 

Combined in a soap, sulphur is used as a wash for 
mangy animals, and as true mange is due to a mite, 
good effects are obtained. Better yet are the results 
when sulphur is administered internally. It is one 
of- the materials eliminated through the skin, and is 
therefore brought into direct contact with the skin 
parasites. 

Among the penetrants the mineral oils rank highest. 
A Hght crude petroleum of the paraffine series, testing 
43° or over on the Beaume scale, will penetrate and 



286 INSECTS 

kill every scale it touches, and it spreads so well that it 
will get under every protection, into every crevice and 
through every covering of plant hairs. Unfortunately 
it goes further and, if carelessly used, is just as likely 
to get through the outer bark into the bast, and to kill 
the tree as well as the insect. Nevertheless the material 
has been and is even yet quite extensively used, and is 
the reliance of a large number of good fruit-growers. 
I do not advise its general use, but mention it for the 
benefit of those willing to try it. In the garden and 
conservatory it has no place. 

Kerosene is a derivative from the crude petroleum, 
with the lighter volatile oils, the vaseline and the par- 
affine eliminated. It can be safely applied to trees 
even when in full foliage, in a very fine spray, under 
conditions which favor rapid evaporation. I have 
frequently applied it with excellent effect late in summer 
on very scaly trees, killing off most of the insects with- 
out appreciable harm to the tree itself. Apple and 
pear trees are most resistant to the mineral oils; peach 
and other stone fruits are most susceptible. Citrus 
trees stand kerosene very well under favorable condi- 
tions; but on the whole this is another material which 
needs a thorough appreciation of all the factors in- 
volved to make it safe. As a winter application it is 
not nearly so effective as crude oil because it evapo- 
rates so much more completely, leaving nothing in the 
way of a coating to continue its work; but that very 
feature makes it safer to use. 

The good points of kerosene as an insecticide were 
long ago recognized, and nearly thirty years ago methods 
of emulsifying it with milk and afterward with soap 
were worked out under the direction of Dr. C. V. Riley 
then U. S. entomologist, by Mr. H. G. Hubbard. The 
milk formula was soon abandoned; but the soap emul- 



THE WAR ON INSECTS 287 

sion stands to this very day, much the same as Mr. 
Hubbard worked it out. 

Kerosene 2 gallons 

Water i gallon 

Hard soap 5 pound 

Shave the soap fine and dissolve in boihng water; 
warm the kerosene and add to the boihng suds; churn 
with a force pump by pumping back into the pail 
through a fine nozzle until a thick white cream is formed. 
This hardens into a butter-like mass when cold and 
may be diluted to any desired extent with water. If 
both kerosene and suds are hot, five minutes' churning 
will bring the proper combination. In making and 
diluting the emulsion, soft water should be used and 
only a little water should be mixed in at first to get 
the butter into soluble form. A well-made emulsion 
will keep for weeks in a dark cool place; but event- 
ually the oil will separate and come to the top. 

Diluted with from twelve to fifteen times its own 
bulk of water this is an excellent summer remedy for 
plant lice, young leaf-hoppers, mites, thrips and other 
insects liable to be killed by contact poisons. The pene- 
trating qualities of the oil and clogging effect of the 
soap are combined; but the soap prevents the rapid 
evaporation of the kerosene, holds it longer in actual 
contact with the vegetation to which it is applied, and 
thereby increases its danger. Most plants will stand 
an application of i to 15; few plants will safely stand 
anything stronger than i to 10, and i to 12 is the more 
usual limit. As a summer wash against scale larvae 
the I to 10 mixture is an excellent combination on all 
save stone fruits, and even i to 15 must be carefully 
used on such. For winter work it is not advised, because 
at a dilution strong enough to kill scales, it is actually 



288 INSECTS 

more dangerous to the trees than the undiluted oil 
itself. Nevertheless, kerosene emulsion shares with 
whale oil soap the burden of the fight against plant lice, 
with the advantage of cost in favor of the emulsion. 

A more recent development in the use of petroleum 
oils is found in the miscible or "soluble" oils, sold 
under special names such as "Scalecide," " Kill-0- 
Scale," "San-U-Zay," or simply as "soluble petro- 
leum." These are preparations of petroleum, crude or 
partly refined, so combined with vegetable or animal 
oils, rosin oil and sulphonated oil, as to be readily 
miscible in water to any extent, forming a perfectly 
homogeneous spraying mixture of even effectiveness 
throughout. None of these oils contain over 75 per 
cent, actual petroleum and few contain over 10 per 
cent, of water, which is actually necessary to form the 
emulsion. They are, therefore, approximately equal 
in their effect and are extremely useful as winter washes 
against scales hibernating in the partly grown condi- 
tion. Against the pernicious or San Jose scale a dilu- 
tion with fifteen parts of water is the weakest mixture 
that should be used in general practice. Good results 
have been obtained with a solutipn of 20 to i, under 
exceptional circumstances; but I would rather recom- 
mend a dilution of only twelve times if I were anxious 
to secure definite effects. These oils have no vaseline 
or paraffine residue, hence can be safely applied for 
successive years, even peach showing no appreciable 
injury within my experience. It is on large old apple 
and pear trees that these miscible oils find their most 
effective field of use, for they spread and penetrate 
well and when applied with proper force can be made 
to reach wherever a scale can go. This quality makes 
them effective against such species as the pear psylla, 
which hibernate as adults in crevices and under rough 



THE WAR ON INSECTS 289 

bark scales, and against such mites as hibernate under 
bud scales or in similar positions. They are not espe- 
cially effective against insect eggs, and have little 
fungicidal value. In all cases where the oils and the 
lime and sulphur are equally effective, the latter is 
preferable because of its influence on plant diseases. 
"Soluble" oils are not safe as summer washes at effec- 
tive strengths, although when carefully applied on 
mature foliage of hardy trees, no serious injury is caused. 

Miscible oils can be made at home and formulas 
have been published minutely describing the process; 
but it requires skill, absolutely uniform materials and 
an outfit that only the user of large quantities can 
afford. Furthermore it is an unpleasant and even 
somewhat dangerous process which can hardly be 
recommended to ordinary farmers and fruit-growers, 
and certainly not to gardeners using only a few gallons 
or even barrels. 

There is another field for kerosene emulsion and the 
hke when it is necessary to reach certain leaf-miners 
which, while feeding on plant tissue are never exposed 
to the action of arsenical coverings, but live entirely in 
the leaf tissue. There is usually, however, an opening 
to the surface, or the tissue above the mine is so thin 
as to be readily penetrated by the oil; hence a contact 
insecticide against a leaf-miner is indicated. 

It is with the mineral oils as with the lime and 
sulphur; the effects are not equally satisfactory under 
all climatic conditions. Applications that are entirely 
safe in one locality may be distinctly injurious to plants 
in another, and a little caution must be observed when 
the material is used for the first time in localities differ- 
ing from those in which it has been tested. 

Another combination with both caustic and pene- 
trating qualities as well as a specific feature of its own 
19 



290 INSECTS 

is found in the resin washes which have had a wide use 
on the Pacific coast, but have not been much exploited 
in the east. Two formulas for summer and winter 
washes are given: 

Summer Formula. 

Resin 20 pounds 

Caustic soda, 70 per cent, or over 5 pounds 

Fish oil 3 pints 

Water sufficient to make 100 gallons 

Winter Formula. 

Resin 3° pounds 

Caustic soda, 70 per cent, or over 9 pounds 

Fish oil 42 pints 

Water sufficient to make 100 gallons 

These are really very thin varnishes, readily soluble 
in water and therefore more effective in a dry climate. 
The second or winter wash contains so much resin that 
its application to foliage would choke and thus destroy 
it and is also much more caustic. The summer wash is 
effective against scale larvae, recent sets, plant lice and 
similar species, clogging their spiracles. 

To make these washes, boil all the ingredients 
together with about twenty gallons of water until 
thoroughly dissolved, adding hot water from time to 
time as needed, but never enough to stop the boiling 
after it has once begun. Three hours will be required 
for a complete mixture, hot water being gradually 
added to make up fifty gallons, stirring continuously. 
After this, the balance of the 100 gallons may be added 
in cold water. It may be that the work of preparing 
these washes has something to do with their present 
lack of popularity. 

It frequently happens that we have underground 
insects such as root maggots to deal with, and none of 
the soap or petroleum washes heretofore considered is 



THE WAR ON INSECTS 291 

of any value in this direction. The petroleum mixt- 
ures, indeed, usually kill the plants primarily and 
the maggots consequentially. We derive some help 
from carbolic acid emulsified with soap, so as to be 
soluble in water. To make this, dissolve one pound of 
hard soap shaved fine, in one gallon of boiling water, 
add one pint of crude carbolic acid (50 per cent.), and 
chum the whole into an emulsion with a force pump. 
This emulsion is diluted for use with thirty times its 
own bulk of water, and applied to the soil at the base of 
infested plants. The mixture, to be efifective, must 
come into direct contact with the insects, hence the 
earlier it is applied when cabbages and onions are 
infested, the more effective it will be; there must be 
enough material to penetrate down to the lowest point 
reached by the maggots. On cabbages this may be 
three or even four inches and may require half a pint of 
material; on onions it would not be over an inch or 
two, and would of course require much less. Wire- 
worms and white grubs are also affected by this emul- 
sion and driven away or killed. On growing foliage it 
cannot be safely applied, and it is unsuitable for use 
against maggots infesting radishes or beets. 

Carbolic acid is sometimes used to increase the 
effectiveness of whale oil soap and an ounce of the 
acid in a gallon of spray mixture does improve it to 
some extent, but not enough to balance the extra cost 
and labor of working it in. It has been added to air- 
slacked lime for use as a repellent around melon and 
other cucurbit vines to keep off the melon beetles. It 
forms an ingredient in tree washes and preparations 
intended to prevent the entrance of borers, and is 
somewhat effective in this direction. But insects are 
not often adversely affected by unpleasant odors unless 
they are also directly poisonous. 



292 INSECTS 

Another use that has been proposed for the acid is 
to paint a band around the trunks of fruit trees with 
the idea that it would be absorbed by the bark and 
carried into the circulation, poisoning the sap to such 
an extent as to kill all the scales and other insects feed- 
ing on the tree. The theory is a very plausible one at 
first sight, but unfortunately the acid as it penetrates 
strikes first the down-current that carries it to the 
roots, and when there is enough of it to get into the 
active cells, these promptly die and refuse to do any 
carrying. If the acid gets still further and really does 
strike the up-current, then the girdling is complete 
and the tree itself dies. Rarely, however, is there 
enough acid applied to cause this mischief. 

This suggests the fact that there are always a num- 
ber of philanthropic gentlemen ready to aid the farmer 
—for a consideration — and willing to insert into his 
trees a compound of which they only possess the secret, 
which will infallibly kill all the insects infesting the tree 
and cure all its diseases. They are even willing to give 
a written guarantee to that effect. Many a farmer 
and tree owner even in cities and towns falls victim 
to the persuasiveness of these benefactors, who bore 
holes two inches deep into the wood, fill them with 
their compound and fasten it in tightly with a wooden 
plug, absolutely beyond reach of those cells of the 
tree -engaged in carrying sap. Even were the material 
soluble and active, it is imbedded in tissue which serves 
only as a support to the tree, and has absolutely nothing 
to do with its nourishment. Its absorption into the 
surrounding cells would therefore mean precisely as 
much as if it were absorbed into the tissues of the 
nearest fence or hitching post. 

Caustic potash and caustic soda have a limited use 
on the farm, but in the orchard and garden are fre- 



THE WAR ON INSECTS 293 

quently used as winter washes for tree trunks. In a 
solution of one pound in one gallon of water we have a 
mixture which kills lichens and' mosses on tree trunks 
as well as many spores of fungi, and leaves the bark 
in a nice, clean, shining condition, vigorous and free 
from all clogging organisms. It is astonishing what an 
improvement a wash of this kind will often produce on 
fruit and shade trees, and where a clean healthy bark 
is a desideratum, there is no better way to obtain it. 
Besides cleaning the bark, this material will also corrode 
and destroy many of the thinner scales such as the 
species of Chionaspis of which the scurfy scale is an 
example. That species hibernates in the egg state, and 
the egg is not affected by the caustic ; but the scale 
covering is thin, easily corroded, and the eggs are then 
washed out and scattered by rains. Those larvae that 
hatch from them will rarely be able to find their way 
back to the tree, and in most instances the eggs them- 
selves perish under the unnatural conditions. A ma- 
terial so caustic as this should be carefully handled, 
for sores caused by it frequently ulcerate badly and 
heal very slowly, because of the destruction of tissue. 

Lime is one of the most useful materials on the 
farm from a great many points of view. Few insects 
care to rest voluntarily on a lime-covered surface; 
only hunger will induce most species to eat through it, 
and some will not touch it under any circumstances. 
Lime in its various forms is about the only material 
used by most European orchardists, and whitewashed 
trees form a characteristic feature in many localities. 
As a whitewash on fences and farm buildings generally, 
inside and out, it covers over or fills crevices and cavi- 
ties that w^ould otherwise serve as hiding places for 
insects. It seals up and destroys the eggs of such insects 
as may be present when the wash is applied, and on 



294 INSECTS 

tree trunks it prevents the setting of young scales. A 
continuous coat of whitewash will absolutely prevent 
the setting of all scales and will keep many of them 
from hatching; but it requires rather a thick coating to 
effect this, for the lifting of the scales when the young 
are ready to emerge, will usually break the coating. 
In chicken-houses the wash should be applied with a 
spray pump so as to force it into cracks and crevices, 
and the addition of a little carbolic acid is here a dis- 
tinct gain to the wash. The same may be said of it in 
stables and out-buildings generally. Instead of the 
crude carbolic acid, which is not readily soluble or mis- 
cible with watery liquids, one of the many soluble tar 
or cresol preparations may be used in liberal quantities. 
Tree trunks are often white-washed to prevent borers 
from entering, and with good effect so long as the 
coating is thick and well put on. But the egg-laying 
instinct is among the strongest, and the parent beetles 
of round, flat-headed and bark borers will hunt for a 
broken point, an unfilled crevice or a loosened bark 
scale, to find a place where they can safely deposit an 
egg, while the clear-wing moths will lay their eggs 
anyway, and trust the minute caterpillar to find a bare 
place or a crevice through which entrance may be 
obtained to the sap-wood below. 

On foHage, whitewash is not an advisable apphca- 
tion; its brittle character makes it quickly imperfect, 
even where the tissue itself is not harmed. 

In its dry condition the range of usefulness of lime 
is much greater. Air-slacked lime mixed with Paris 
green for application through a blower or powder bel- 
lows is well known, and as a driver in fields of cucurbs 
invaded by the cucumber beetles, it is relied upon in 
many parts of the country. As a dry hydrate, that is 
slacked with just enough water to crumble it into a dry 



THE WAR ON INSECTS 295 

powder, it is useful against a great variety of viscid or 
moist slugs, like those of the asparagus, potato, pear and 
the like. When slacked in this way the fine particles of 
lime are still very caustic and need another particle of 
water to complete the slacking. If, in this condition, the 
lime is dusted on the moist slugs, each particle of lime 
gets the desired particle of water from the body of the 
slug, and in doing so burns a little hole into the skin. 
The effectiveness of a dry lime application, therefore, 
depends on the moist condition of the insect to be 
dealt with, and in consequence early morning appli- 
cations when there is a little dew are always most 
effective. In the asparagus fields where once the slugs 
have gotten a start after the cutting season is over, 
there is nothing better than a cloud of dry hydrate of 
lime put on with a powder gun just at sunrise or a little 
before. 

This reference to the time of application in order to 
reach the insects in the best condition brings to mind 
that there are some plants and insects that by reason 
of a waxy or powdery surface or covering repel or shed 
water particles. The woolly lice and mealy bugs are 
insect examples and the cabbage leaves are good plant 
examples. When cabbage plants are attacked by 
Aphids which have a covering of fine waxy powder, 
ordinary watery applications are of little or no use, 
and even soap washes or kerosene emulsions must be 
applied with considerable force and in a fine spray to 
really wet and be effective. W^hen on cabbage or simi- 
lar plants arsenical applications are required, the 
matter becomes even more difficult and some sort of 
adhesive is needed. Molasses, glucose and soap add 
materially to the sticking qualities of arsenical sprays 
other than arsenate of lead; but in extreme cases a 
resin soap is needed. Such resin soap may be pur- 



296 INSECTS 

chased, or may be made up according to the following 
formula : 

Pulverized resin 5 pounds 

Concentrated lye i pound 

Fish oil I pint 

"Water 5 gallons 

Boil resin and oil in one gallon of water until the 
resin is thoroughly softened, then dissolve and add the 
lye slowly, stirring continuously until thoroughly mixed. 
Then add four gallons of water and boil for about two 
hours or until you get a clear amber-colored liquid which 
dissolves readily in cold water. This liquid resin soap 
may be added at the rate of one gallon to every 100 
gallons of any arsenical spraying mixture other than 
arsenate of lead, or at the rate of one gallon for every 
fifty gallons of any spray used on cabbage or similar 
waxy leaves. The adhesive should be placed in the 
entire amount of water to be used and, when thor- 
oughly dissolved, the Paris green or other poison should 
be added. 

Powdered white hellebore was at one time almost 
the main reliance against saw-fly larvae such as the 
currant worm, and is even yet the favorite for this 
purpose with many gardeners. It may be applied as a 
dry powder, pure or mixed with two or three times its 
own weight of cheap flour; or it may be used in the 
form of a decoction, using one ounce, steeped in two 
quarts of hot water. This is also effective against 
certain small caterpillars and naked slugs, but is not so 
reliable and is more expensive than some of the other 
materials already recommended. 

Sometimes we can make use of certain abnormal 
tastes among insects to secure their destruction. Thus 
cut- worms prefer wheat bran to their normal food, 



THE WAR ON INSECTS 297 

and will eat it by choice even when a corn plant grows 
near by. We take advantage of this habit by making 
up a mixture of 'white arsenic one pound, to wheat 
bran seventy-five pounds; mingle thoroughly, moisten 
■with sugar water enough to make a soft mush and put a 
spoonful in the hill of plants to be protected. There 
will be dead cut-worms next morning, and no further 
cutting of plants. Sometimes, where a field of grass 
has been plowed down and cut-worms are known to be 
present, rows of the dry bran and arsenate mixture are 
drilled at ten-foot intervals across the field to attract 
and destroy the worms before the crop is set out or is 
up, as the case may be. Paris green may be used in- 
stead of arsenic, but the latter is cheaper. Chickens or 
other farm animals liable to eat this poisoned bran 
should of course be kept out of fields so treated. 

Grasshoppers of certain injurious species have an 
abnormal fondness for moist horse manure and great 
numbers can be killed off by mixing one pound of 
arsenic with three gallons of droppings and spreading 
where the insects are most numerous. It is better to 
use small quantities several days in succession than 
large quantities at one time, because as the material 
dries out it loses its attraction. 

To keep borers out of fruit and shade trees, all sorts 
of mechanical protections have been devised. The use 
of lime-wash has been already referred to, and that is 
most wide-spread. Sometimes soap, carbolic acid and 
arsenic are added, and help a little toward its effective- 
ness, because the poison may kill the parent beetles 
when cutting a place for the egg, or the young larvae 
when attempting to enter. Sometimes the entire trunk 
is cased in wire mosquito netting held at a distance of 
at least half an inch from the bark at all points, and 
sometimes only the lower portion of the trunk is so 



298 INSECTS 

protected. The round-headed borers of pomaceous 
fruits like apple and quince, and the boring caterpillars 
infesting peach and its allies, usually enter near the 
surface and work in just at or below the ground. A 
wash of hydraulic cement mixed with water, or better, 
with milk, is often used to protect trees at this point 
and on peach trees a band of newspaper or tar paper is 
tied so as to extend a little below the surface and for a 
distance of eighteen inches above. Other mixtures have 
been recommended and all are more or less effective. 
It means simply coating the bark with anything that 
the insects cannot or will not penetrate in their efforts 
to get to their place of feeding. 

Gas tar is safely used in some localities as a protec- 
tion, but in others is fatal to the trees, and it is better 
not to use tar paper or any black paper, since that 
seems to cause a scalding of the bark beneath it. So, 
while paints mixed with linseed oil are tolerably safe, 
those in which turpentine is used should be avoided, 
as they are almost always dangerous. 

A great variety of protective devices are in use on 
trees to prevent insects from getting up or down the 
trunk, or to attract them as shelter for larvae and 
pupse, and some of these are effective in special cases, 
as when a band of fluffy cotton or of a sticky material 
bars the ascent of female canker-worm moths or the 
ascent of caterpillars of the tussock moths, from egg 
masses laid below them. The larvae of codling moths 
can be attracted to burlap bands when they leave the 
fruits to pupate, and many of them can be there gathered 
and destroyed. Finally, on field crops we can use, very 
effectively, tar paper discs to protect cabbage plants 
from root maggots. 

The direct campaign with poisons is a most impor- 
tant feature of the war with insects, and to carry it on 



THE WAR ON INSECTS 299 

we need a great variety of machinery for applying pow- 
ders and liquids, and such machinery is now obtainable 
almost throughout the civilized world, to meet the needs 
of the man who wishes to protect one plant as well as of 
him who farms ten thousand acres. There is every 
range from the little atomizer to the steam pump, and 
from the little powder bellows to the rotary fan blower 
capable of enveloping a large tree in a dust cloud. Spe- 
cific description of such machinery would be of little 
avail, and he who has the selection need keep in mind 
only a few fundamental points. The apparatus should 
be so simple as to be fully understood by the pur- 
chaser; it should be well made and of the most durable 
material; it should be more than equal to the utmost 
demands ever made on it; it should be able to give 
great force to the material issuing from spout or nozzle, 
and there should be a nozzle or spout capable of bring- 
ing the dust or liquid into actual contact with all the 
insects to be reached, under all the circumstances 
under which they occur. Thoroughness of application 
is always essential to success, and careless work is al- 
ways wasteful and expensive work. 

We are not confined in our work to insecticides 
merely. Modifications of the primitive method of col- 
lecting potato beetles in tin pans with a scum of kero- 
sene are still in use, and in some cases form our only 
practical line of offense. Leaf-hoppers and grass- 
hoppers are collected by means of hopper-dozers drawn 
by man or horse power over infested fields, gathering 
up the insects on a bed of soft tar or petroleum. We 
have similar contrivances to run under grape vines 
into which we jar rose-chafers, and wheeled, umbrella- 
like structures to capture plum curculios. In a few 
cases when large, conspicuous caterpillars like those of 
the hawk-moths infest low plants like tobacco or toma- 



300 INSECTS 

toes, hand picking is the best and most reHable method. 

So, when borers get into om- peach trees, the only 
really effective way is to go after them with a knife, 
and if apple or similar round-headed borers are in 
fault, a soft wire is added to the outfit to reach such 
insects as have gotten into the heart wood. 

Against species that march we erect barriers of one 
kind or another. Army-worms and chinch-bugs, for 
instance, may sometimes be stopped by running a 
ditch across their path or a couple of plowed furrows 
with steep sides to prevent their easy ascent. At 
intervals in these furrows post holes are driven and as 
the insects crawl along the bottom of the furrow or 
ditch seeking a way out, they fall into the post holes 
and are treated to a dose of kerosene. Myriads of 
specimens are often killed off in such campaigns, and 
the farmer saves his crops, without perceptibly de- 
creasing the number of his foes for the year to come. 

Some species we are able to circumvent by a httle 
adaptation of our farm practice. For instance, where 
com is raised continuously on the same land in the 
middle west, the corn-root worm soon becomes a serious 
pest; but if every third year the land is put into some 
other crop, no harm ensues because the insects in the 
old cornfields are starved out. We have learned that 
rotation of crops is a good thing, and try to avoid plant- 
ing two successive crops of a similar kind; or if that 
cannot be avoided, planting or plowing so as to avoid 
harm. For instance, corn following old timothy is bad 
practice where the latter is liable to be infested with 
bill-bugs. Corn belongs with the grasses, and the bill- 
bugs finding no timothy when they emerge, attack the 
corn. If the succession cannot be avoided, the soil 
should be plowed in fall and the com planted as late as 
may be. Similar practice is to be followed where root 



THE WAR ON INSECTS 301 

web-worms occur and, as a rule, old sod is better fall- 
plowed if insect injury to the next following crop is to 
be avoided. Most wire-w^orms and white grubs require 
two entire years to come to their full growth, pupating 
or even changing to an adult in the late fall of the 
second year, and coming out as adults during the 
spring of the third. Fall plowing at the end of the sec- 
ond year will expose these pupae or recent adults and 
kill them, w^hereas if delayed until the land is fit the 
spring following, the beetles would be sufficiently mature 
to survive. 

The corn-worm and many similar pests also pupate 
in the fall, making cells in which they lie safely in all or- 
dinary winters. Fall-plow^ing breaks up those cells and 
brings the soil into direct contact with the pups, which 
are killed by the contractions and expansions of the 
soil about them, under the influence of frost and thaw. 
Of course fall-plowing is not always good farm prac- 
tice from other points of view, and the grower must 
decide what he had better do after balancing all the 
factors of his problem. But in the control of under- 
ground pests this practice is important. Sometimes, 
indeed, our efforts are indirect, as when in late fall we 
plow land infested with root-lice very deeply, to destroy 
the nests of the ants that shelter them or their eggs 
during the winter. 

Frequently the time of planting or the time or 
manner of harvesting determines the question of in- 
jury. We have learned that in regions subject to Hes- 
sian fly attacks, late-sown wheat may be almost en- 
tirely free from infestation, while that sown early may 
be almost totally destroyed. This is because the early 
fall rains bring the adult flies to maturity and they lay 
their eggs on wheat or other grasses very soon there- 
after. Anything that comes up later is exempt from 



302 INSECTS 

attack. It is impossible to fix an arbitrary date, for 
that varies with latitude, and even in the same latitude 
the time at which the flies appear on the wing is deter- 
mined by weather conditions: a drought may delay 
them until the very latest period for safe sowing has 
passed, and in that case early and late sown are apt to 
be equally infested. Sweet potato growers in regions 
infested by flea beetles have learned that if they delay 
setting out their plants until the middle of June they 
have little to fear from the insects; but if plants are 
set in May, they are almost certain to be seriously 
injured. Other cases might be cited, but it is sufficient 
to show that by a careful study of the habits of a species 
we can often avoid injury without a direct fight. Wheat 
harvested in July and left in shock is very likely to 
become infested by the Angoumois grain moth. Carted 
from shock to mow the infestation spreads until, in 
September or October when threshing time comes round, 
a large percentage of grain is defective and "flies" or 
"moth" are numerous. If instead of being left in the 
fields and then mowed, the grain had been at once 
threshed and binned, there might have been a little 
surface infestation, but there could have been no serious 
spread in the bulked grain. 

Occasionally an insect can be diverted from a more 
to a less valuable crop, as in the case of the squash 
borer which prefers late squashes like the hubbard or 
marrowfats when it can get them, but will accept sum- 
mer varieties like the crook-neck if the others are not 
present in equal attractiveness. The grower therefore 
plants crook-necks early, and on the same ground puts 
in the other varieties late. The early vigorous growers 
attract the moths, the plants become infested but are 
vigorous enough to produce a crop that pays for the 
labor, before the late varieties need the ground and the 



THE WAR ON INSECTS 303 

borers approach full size. Then the infested plants are 
taken out and destroyed, borers and all, leaving the 
others free with prospects for only a very small brood 
of moths for next season. 

That introduces the matter of clean culture. It 
has been shown, elsewhere, that some of our well-known 
pests pass a portion of their life, and sometimes an im- 
portant one, on wild plants allied to the crop grown, 
and these serve to tide it over from one season to an- 
other. Clean cultivation rids the farm or garden of 
these wild plants and makes it more difficult for them 
to survive. So a great many species live through the 
winter on the remnants of the crop they infested, and 
were these destroyed, the hibernating forms would be 
destroyed with them. It is a good general rule, when 
you are done with a crop, get it off as soon as possible 
and burn all left-overs that might shelter injurious 
insects. Stems of cotton, cucurbs, potatoes and toma- 
toes are among those with insects so controllable. 

If in all orchards all dropped fruit could be kept 
picked up and destroyed, injury from codling moth 
would be at once reduced more than one-half; plum 
curculios would soon cease to be important, and fruit 
flies would lessen materially. Some work is done along 
this line in large orchards, but as a rule the insects in 
dropped fruits are allowed to develop at will. 

Farm animals can be utilized much more exten- 
sively than they have been. Sheep and hogs in an 
orchard are great helps in disposing of dropped fruits 
and of such insects as come to the surface. A drove 
of hogs in a sod field infested with wire-worms and 
grubs will tear it up and dispose of a very large number 
of the specimens if aided by a few shallow furrows to 
give them a start. Chickens, turkeys and guineas are 
great insect feeders and can be trained to follow the 



304 INSECTS 

plow and pick up every specimen brought to view. 
Once a small number of fowls has been trained to this 
work, the flock will continue the training; the new 
members following the older without additional trouble 
to the farmer. 

In the selection of fertilizers considerable benefit 
is sometimes derived in the use of minerals rather 
than barn-yard manure. Many insects require the 
shelter or presence of decaying vegetable material, 
and do not thrive in soils impregnated with mineral 
fertilizers. This is a point, however, where the question 
of farm practice is eminently one for the cultivator, and 
no general recommendations can be given. 

There are still among our battery of insecticides 
the gases and vapors, and these are of great impor- 
tance. Sulphur fumes have been used for many years 
against household insects but these are being superseded 
by the hydrocyanic acid already described. 

Bisulphide of carbon is a clean, water- white liquid, 
very foul in smell, volatilizing rather slowly at ordinary 
temperatures, the vapor heavier than air and very 
inflammable. This vapor is fatal to most insects ex- 
posed to it in a confined space for an hour or more, 
and it destroys the vitality of seed germs exposed to 
it much over twenty-four hours. It is rarely used in 
the field, but for insects infesting stored products is 
extremely useful. Where entire plants infested by plant 
lice can be covered by a tight cone, jar or box, one 
drachm or, roughly speaking, a tablespoonful to every 
cubic foot of space will kill the insects in one hour. 
In melon or cucumber fields in which plant lice have 
just made a start, it is sometimes possible to check their 
spread by treating the infested hills under hay-caps 
or similar covers, or even under tubs or large pails. 
Large clam-shells make good receptacles for the liquid, 



THE WAR ON INSECTS 305 

and as the vapor is heavy, the shell should be put on 
top of the mass of vines. 

A much more usual employment for the material 
is to destroy insects infesting seeds like peas, beans, 
lentils, wheat or corn. In such cases the infested seeds 
should be put into a tight box or other receptacle, and 
bisulphide at the rate of one drachm per cubic foot 
of space should be placed in a shallow dish on top of 
the mass, the box or jar being tightly covered, of course. 
In twenty -four hours all the insects will be killed with- 
out injury to the germinating power, but if the seed 
is to be used for planting, it must then be aired out be- 
fore being again put away. Eggs are not killed by this 
vapor, hence it may be necessary to treat a second time 
in case of badly infested material. If the grain or other 
seed is to be used for food only, it may be kept covered 
indefinitely, as no injury is caused to its milling or cook- 
ing qualities. In large spaces one pound may be counted 
for 100 cubic feet of space, or for one ton of binned 
grain. Shallow vessels should always be used for evap- 
orating dishes to expose as large a surface as possible, 
and the heavy nature of the fumes must be taken into 
consideration. Under no circumstances should the 
material be used near a light of any kind, and if the 
person using it has any regard for his safety, he w^ill 
not smoke while handling it even in the field. 

Before the development of the hydrocyanic acid 
gas, bisulphide of carbon was used to treat even large 
spaces like houses, bams and mills; but its cost and 
dangers are so great compared with the newer material 
that it is not now employed in this way. Purchased 
in small quantities at drug store prices, this is rather 
an expensive material; but there is a special much 
cheaper grade known as "Fuma" bisulphide, which 
answers every purpose for agricultural use. 



3o6 INSECTS 

Hydrocyanic acid gas is produced by the action of 
dilute sulphuric acid on cyanide of potassium, and is 
intensely poisonous to all animal life. It effects vege- 
table life to a somewhat less extent and more slowly, 
so that there is usually a fair margin of safety between 
its effectiveness on insects and the danger of injury on 
plants. For the destruction of insects on dormant 
nursery stock, and for the treatment of rooms and 
buildings to destroy household or other pests, the fol- 
lowing formula answers for loo cubic feet of space: 

Cyanide of potassium, 90% pure (by weight) ... i ounce 

Sulphuric acid, sp. gr. 1.83 (by measure) 2 ounces 

Water 4 ounces 

The gas is lighter than air and is generated in an 
earthenware jar, pot or basin as follows: First pour in 
the water, add the acid slowly, and finally drop in the 
cyanide broken into small lumps in a thin paper bag. 
The order of mixing is important, for if the water be 
poured into the acid, the amount of heat suddenly 
developed will be so great as to spatter the material 
in every direction. The cyanide is dropped in, bag 
and all, to somewhat delay the development of gas and 
permit the operator to escape or close the fumigating 
chamber. The method of dealing with household pests 
has already been given. Greenhouse fumigation forms 
a study by itself, because of the difference in efifect on 
the many sensitive plants there raised, and for which 
no generally applicable directions can be given. 

Orchard fumigation is not much practised in the 
east where most of the trees have a dormant season 
permitting their treatment with sprays. On the Pacific 
coast, fumigation of citrus and olive trees is quite largely 
practised and elaborate apparatus for covering trees 
with gas-tight tents is in use. But even there the prac- 



THE WAR ON INSECTS 307 

tice is not yet finally settled, and an extensive series 
of experiments is in progress to determine the most 
effective methods. Under these circumstances no 
more is needed here than a reference to the matter, 
emphasizing its extent and importance. 

By no means all the materials used in the fight against 
insects have been enumerated here; a few, like gasoline 
and Delphinium are of very limited application and 
have been referred to in other connections. But enough 
has been said to show the chief weapons in our battle 
with the tiny foes that influence us so much more than 
is generally known. What is not told is the number 
of materials and combinations that have been tried 
and rejected, before those here enumerated were fully 
tested out and approved. In the reports and bulletins 
of agricultural departments and experiment stations, 
almost every year brings records of trials made of new 
combinations; some originated by the experimenters, 
some produced by inventors or manufacturers who 
believed they had discovered something better than 
was ever known before. Out of all these experiments 
very little is annually added to our battery; but 
the limitations of the older materials are becoming 
ever better understood and the number of effective 
combinations is larger now than ever before. 

And so in the machinery for applying insecticides 
and fungicides there is an enormous and continuing 
progress. A collection of dusters and sprayers dating 
only ten years back now seems antiquated and ineffec- 
tive, and as our methods of application become perfected, 
the benefits derivable increase. 

From the practical standpoint man now carries on 
his war against insects absolutely without regard to 
the natural checks of that insect, if it be a native. If 
it be an introduced species his attempt is to restore the 



3o8 INSECTS 

natural balance by introducing the natural checks as 
well, and beyond that he relies on his own efforts. 

We have learned to take advantage of the weak 
points in the life cycle of a troublesome species, and 
we know that there is at least as much in the proper 
application of insecticides as in the insecticides them- 
selves. As there is a continuous specialization in the 
raising of crops, so each grower learns to deal with the 
pests of that crop by experiment and observation. 

It is beginning to be realized that numbers of speci- 
mens are not a measure of the difficulty in dealing 
with pests. Mosquitoes are abundant enough in exam- 
ples, but their Hfe cycle is simple and the methods of 
control are obvious. The old cry "it can't be done" 
has not even yet ceased, in the face of the results ob- 
tained in Cuba, Panama, and New Jersey. And yet, 
after all, it is simply a matter of dealing with many 
breeding places in the same way, and when a problem 
is reduced to a mere matter of amount, it is a matter 
of time and dollars only to get it done. 

Flies are even more universally distributed than 
mosquitoes, and from the sanitary standpoint yet 
more dangerous; but even they will not escape man's 
efforts at control. The campaign has been already 
begun and no doubt it will be continued until practical 
measures for checking fly development are universal. 

To one in the forefront of the battle progress some- 
times seems distressingly slow, and results small out 
of all proportion to the efforts made; but, after all, 
a review extending back a decade or two shows that 
neither the entomologist nor those for whom he has 
labored need be ashamed of the advances made. At 
all events the importance of insects in their relation to 
man has come to be fully realized. 



INDEX 



Adhesives, 295 
Air-slacked lime, 294 
Angoumois grain moth, 242, 

302 
Animal feeders on insects, 131 
Anopheles and malaria, 204 

habits, 2 1 1 
Ant guests, 128 

lions, 89 
Ants and plant lice, 125 

and Scutellista, 127 

as scavengers, 190 

domestic economy, 125 

in houses, 242 
Aphelinus on scales, 119 
Aphis lions, 89 
Apple borers, 65 
Argentine ant, 245 
Arsenate of lead, 274 
Arsenical poisons, 274 
Asiatic lady-bird, 107 
Asilidse, no 

Balance of nature, 249 
Banding, uses of, 298 
Bark-beetle injury, 70, 268 
Barriers to canker worms, 298 
Bat-tick, 183 
Bean weevils, 66, 261 
Beaver parasite, 161 
Bed-bugs, 229 
Bee disease, 151 

flies, no 

habits, 26 

products, 195 
Bees as pollenizers, 25 



Beetles as borers, 267 

as parasites, 96 

as pollenizers, 36 

injury by, 58 
Bill bugs, 259 
Bird lice, 160 
Birds vs. insects, 133 
Bisulphide of carbon, 304 
Biting lice, 159 
Black beetles, 227 

flies, 167 
Blastophaga on figs, 31 
Blister beetles, 97, 197 
Blood of insects, 10 
Blow-fly, 175 
Blue-bottle fly, 174 
Body louse, 156 
Boll -worm, 263 
Bombyliid^E, no 
Book lice, 221 
Bordeaux mixture, 275 
Borers as food, 197 

protections from, 297 
Boring caterpillars, 266 
Bot-flies, 176 
Bran and arsenic, 297 
Breathing of insects, 10 
Breeding of insects, 1 5 
Bristle-tails, 219 
Bruchidje, 66, 261 
Buffalo gnats, 166 

moth, 233, 234 
Bumble-bees and clover, 25 
Buprestida;, 60 
Burying beetles, 188 
Butterflies as pollenizers, 34 



309 



3IO 



INDEX 



Cabbage maggot, 82 
Caddice-flies, 91 
Cantharides, 197 
Carbolic acid, 291 
Carbon bisulphide, 304 
Carpenter worms, 74 
Carpet beetles, 233 
Carrion beetles, 188 
Caterpillar diseases, 149 
Cattle bots, 180 
Caustic potash, 292 

soda, 292 
Cecidomyiid injury, 81 
Centipedes in house, 218 
Cerambycidffi, 64 
Chicken flea, 165 

lice, 160 
Chilocorus bivulnerus, 106 

similis, 106 
Chinch-bug disease, 145 

injury, 53 
Chitin, 16 

Cholera and flies, 199 
Chrysanthemum fly, 37 
Chrysomelidas, 64 
Chrysopidae, 8g 
Cicada disease, 148 

injury by, 52 
Cigarette beetle, 237 
Circulatory system, 10 
Clavicom beetles, 187 
Clean culture, 251, 303 
Clerids W5. Scolytids, 108 
Click beetles, 59 
Climate and insects, 138, 144 
Clover pollination, 25 
Clothes moths, 238 
Coccinellidae habits, 102 
Cochineal, 196 
Cockroaches, 227 
Codling moth, 262 
Coleoptera, 18 



Coleoptera, as parasites, 96 
as pollenizers, 36 
injury by, 58 
Coleopterous borers, 267 
Complete metamorphosis, 17 
Contact poisons, 276 
Com bill-bugs, 259 

worm, 263 
Cossids, injury by, 73 
Cotton-boll weevil, 141, 261 
Cottony cushion scale, 105 
Crab louse, 158 
Crane-flies, 80 
Crickets in house, 225 
Crop remnants, 303 
Croton bugs, 227 
Crude petroleum, 285 
Culex and disease, 207 
Culicide, 213 
Currant worm, 77 
Cutting out borers, 300 
Cut -worm injury, 259 
Cynipid injury, 78 

Deer flies, 169 
Dermestidas, 189 
Dermestids in house, 232 
Destroy crop remnants, 303 
Digger wasps, 116 
Diptera, 20, 190 

as pollenizers, 37 

injury by, 80 

predatory, 109 
Diseases and insects, 199 

of insects, 138, 144 
Dragon flies, 92 
Drug beetle, 237 
Dry hydrate of lime, 294 

powders, 276 

Ears of insects, 13 
Earwigs, habits of, 53 



INDEX 



311 



Egg stage, 15 
Elateridag, 59 
Ephemeridae, 87 
Eyes of insects, 13 

Factors favoring insect injury, 

251 
Fall plowing, 301 
Fallen fruits, 303 
Farm animals, use of, 303 

practice, 300 

and insect injury, 259 
Fecundity of insects, 84 
Feeling, sense of, 13 
Fertilizers for insect control, 

304 
Fifteen-spotted lady-bird, 104 
Figs, pollination of, 30 
Filariasis and mosquitoes, 207 
Fish-moths, 219 
Flat-head borers, 60 
Fleas, 162 

as disease carriers, 213 

development of, 215 
Flies and sleeping sickness, 208 

as disease carriers, 199 

as pollenizers, 37 

as scavengers, 190 

blood-sucking, 166 
Flour beetles, 236 
Fly disease, 144 
Foul brood in bees, 151 
Fowls 1^5. insects, 137 
Fruit flies, 83 
Fumigating dwellings, 246 
Fumigation, 306 

for mosquitoes, 213 
Furrows as barriers, 300 

Gall midges, 80 

wasps, 77 
Galls, uses for, 197 



Gas-tar protectors, 298 
Geographical distribution, 139 
Golden -eyed flies, 170 
Grape phylloxera, 252 
Grasshopper disease, 144, 147 

injury, 54 
Grasshoppers as food, 196 
Green-heads, 169 
Ground beetles, loi 

Hand picking, 299 
Head lovise, 156 
Hearing of insects, 13 
Heart of insects, 10 
Hellgrammite, 88 
Hellebore as insecticide, 296 
Hemiptera, 18 

as animal parasites, 153 

feeding habits, 41 

habits of, 93 
Hepialid injury, 74 
Hessian fly, 81 
Heteromera, food habits, 67 
Histerid^E, 189 
Honey bees, 195 

dew, 256 
Hopper dozers, 299 
Horn-fly, 171, 254 

-tails, injury by, 77 
Horse bot, 178 

flies, no, 169 

manure and arsenic, 297 
House ants, 242 

fly, 200 

mosquito, 208 
Household insects, 217 
Hydrocyanic acid gas, 246, 306 
Hymenoptera, 20 

injury by, 75 

predatory and parasitic, 

115 
Hyper-parasitism, 124 



312 



INDEX 



Incomplete metamorphosis, 1 7 
Indian-meal moth, 242 
Injury caused by insects, 269 
Insect powder, 276, 277 
Insecticide machinery, 299 
Insects as disease carriers, 199 

as food, 196 

as medicine, 197 

defined, 10 
Instars =^ stages, 1 5 
Introduced insect pests, 252 

plants, 252 

Jigger flea, 163 
June bugs, 63 

Katydids, 57 
Kerosene, 286 

emulsion, 287 

Lace-wing flies, 89 
Lace-insects, 195 
Lady-bird beetles, 102 
Lamellicornia, 62 
Lampyridae, 108 
Larder beetles, 189 
Larval stage, 15 
Leaf -feeding insects, 258 

hoppers, injury by, 257 
Lepidoptera, 20 

as parasites, 161 

as poUenizers, 34 

injury by, 72 

predatory, 109 

Machinery, 299 
Malaria, how carried, 203 
Mantids, habits of, 95 
MantispidtE, 90 
May beetles, 63 
flies, 87 



Meadow grasshoppers, 56 
Meal snout-moth, 242 

worms, 235 
Mecoptera, 90 
Meloidte, habits of, 97 
Metamorphoses, 15 
Midges, 167 

injuries by, 261 
Migration of insects, 140 
Mineral oils, 285 
Miscible oils, 288 
Moisture, effect of, 142 
Moulting of insects, 1 5 
Mosquitoes and malaria, 204 

and yellow fever, 206 
Moths as pollenizers, 34 
Muscles of insects, 12 
Museum beetles, 234 
Myrmeleonidae, 89 

Neuroptera, 18, 88 

feeding habits, 41 
Nervous system, 12 
Nut weevils, 67, 262 
Nymph, 17 

Odonata, habits, 92 
QJstridse, 176 
Onion maggot, 82 
Oriental roach, 227 
Orthoptera, 18 

injury by, 53 

Ox-bot, 180 

Pain, sense of, 14 
Paper disks for root maggots, 
298 

protectors for trees, 298 
Parasitic flies, 113 

hymcnoptera, 120 
Parasitism on vertebrates, 153 
Paris green, 274 



INDEX 



3^3 



Pea weevils, 66, 261 
Peach-tree borer, 72 
Pear midge, 81, 254, 262 
Perception, sense of, 14 
Periodical cicada, 52 
Phasmids, injury iDy, 53 
Phylloxera, 252 
life cycle, 46 
on grape, 46 
Pill beetles, 189 
Pirate bugs, 94 
Plague and fleas, 214 
Plant -beetle injury, 63 
lice and ants, 125 

and weather, 143 
development, 43 
disease, 148 
injury by, 42, 255 
parasites on, 119 
remedies, 277 
sexual parts, 2 r 
Planting, time of, 301 
Plasmodium, 203 
Platypsylla, 161 
Platyptera, 87 
Plecoptera, 87 
Plum curculio, 262 
Pollination by insects, 22 

by wind, 22 
Polyembryony, 122 
Pommace flies, 191 
Potato beetle, 249 
Potter wasps, 116 
Powder-post beetles, 238 
Predatory beetles, 100 

insects, 86 
Pronuba and yucca, 24 
Protective resemblance, 131 
Psorophora, log 
Psocids in house, 221 
Ptinids in houses, 237 
Pupal stage, 16 



Pupipara, 182 
Pyrethrum, 277 

Raphidiidse, 90 
Reason in insects, 14 
Reduviids, habits of, 94 
Reproduction, organs of, 15 
Resin soap, 296 

washes, 290 
Rhynchophora, 67 
Roaches, habits of, 95, 226 
Robber flies, no 
Root lice, 46 

maggots, 82 
Rose-chafer injury, 258 
Rotation of crops, 300 
Round-head borers, 64 
Rove-beetles as scavengers, 
187 
habits of, 102 

San Jos^ scale, 51 
Saw-fly injury, 76 
Scale-insect disease, 147 

injuries, 49, 256 
Scale insects, development, 49 
Scales, parasites on, 119 

remedies for, 280 
Scavengers, insects as, 185 
Scolytid, injury, 70 
Scorpion flies, 91 
Screw-worm fly, 173 
Senses of insects, 13 
Sesiids, injury by, 72 
Sheep-bot, 177 

ticks, 182 
Sight of insects, 13 
Signate lady-bird, 105 
Silk-worm disease, 151 
Silk-worms, 192 
Silver-fish, 219 
Simuliida?, 166 



314 



INDEX 



Sinviate pear borer, 254 
Skin of insects, 16 
Smell, sense of, 13 
Smilia misella, 106 
Snout -beetle injury, 67 
Soaps as insecticides, 278 
Soldier beetles, 108 
Soluble oils, 288 
Squash borer, 72, 302 
Structure of insects, 9 
Stable flies, 171 
Staph ylinidEe, 187 

habits of, 102 
Stegomyia and yellow fever, 
206 

habits, 210 
Stem borers, 265 
Stone flies, 87 
Stylops, habits of, 96 
Sulphur as an insecticide, 285 

soap, 285 
Syrphids vs. plant lice, 1 1 1 

Tabanidas. no, 169 
Tachinid flies as parasites, 113 
Tactile structures, 14 
Taste, sense of, 13 
Temperature, effect of, 140 
Termites in house, 222 
Thalessa, habits of, 121 
Thripids and dry weather, 142 
Thysanura, 17 

feeding habits, 40 
Thysanurids in house, 219 
Time of planting, 301 
Tobacco, 277 
Tracheae, 10 



Transformations, 15 
Trap crops, 302 
Tree-hoppers, injury by, 52 

protectors, 298 
Trichoptera, habits, 91 
Tsetse flies, 207 
Tumble-bugs, 189 
Typhoid fever and flies, 200 

Vedalia cardinalis, 105, 253 
Vertebrate enemies of insects, 
130 

Walking sticks, 53 
War on insects, 271 
Warbles, 180 
Warning colors, 132 
Wasps, predatory, 115 

social, 1 18 

solitary, 115 
Weather i'5. insects, 13S 
Whale-oil soap, 279 
Wheel-bug, 94 
White ants in house, 222 

fly in California, 141 

grubs, 63 
Winter, effect of on insects, 

143 
Wire -worms, 59 
Wood-boring beetles, 60 

-leopard moth, 73 
Woolly apple louse, 257 

Yellow fever and mosquitoes, 

206 
Yucca pollination, 23 



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Our insect friends and enemies